U.S. patent number 10,424,343 [Application Number 15/845,404] was granted by the patent office on 2019-09-24 for imaging device and playback device.
This patent grant is currently assigned to CANON KABUSHIKI KAISHA. The grantee listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Fumihiro Kajimura, Masafumi Kimura, Akihiko Nagano, Go Naito, Makoto Oikawa, Yasuo Suda, Koichi Washisu, Ryo Yamasaki.
View All Diagrams
United States Patent |
10,424,343 |
Kimura , et al. |
September 24, 2019 |
Imaging device and playback device
Abstract
An imaging device includes an imaging element that acquires a
first image based on signal charge generated during a first
accumulation time, and a second image based on signal charge
generated during a second accumulation time relatively longer than
the first accumulation time and synchronized with the first image
during a synchronization period including the first accumulation
time, and a moving image file generating unit that generates a
moving image file including a first moving image based on the first
image, a second moving image based on the second image, and
synchronization information for synchronizing the first moving
image and the second moving image frame by frame.
Inventors: |
Kimura; Masafumi (Kawasaki,
JP), Suda; Yasuo (Yokohama, JP), Washisu;
Koichi (Tokyo, JP), Nagano; Akihiko (Ichihara,
JP), Yamasaki; Ryo (Tokyo, JP), Oikawa;
Makoto (Yokohama, JP), Kajimura; Fumihiro
(Kawasaki, JP), Naito; Go (Kawasaki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
N/A |
JP |
|
|
Assignee: |
CANON KABUSHIKI KAISHA (Tokyo,
JP)
|
Family
ID: |
58317748 |
Appl.
No.: |
15/845,404 |
Filed: |
December 18, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20180158487 A1 |
Jun 7, 2018 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
15258564 |
Sep 7, 2016 |
9881648 |
|
|
|
Foreign Application Priority Data
|
|
|
|
|
Sep 9, 2015 [JP] |
|
|
2015-177587 |
Jun 23, 2016 [JP] |
|
|
2016-124714 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N
1/212 (20130101); H04N 5/232939 (20180801); H04N
9/04557 (20180801); G11B 27/105 (20130101); H04N
5/772 (20130101); H04N 5/23245 (20130101); H04N
9/045 (20130101); H04N 5/232933 (20180801); H04N
9/8042 (20130101); H04N 5/35554 (20130101); H04N
5/3745 (20130101); H04N 5/355 (20130101); H04N
5/35563 (20130101); H04N 5/9205 (20130101); H04N
5/369 (20130101); H04N 2101/00 (20130101) |
Current International
Class: |
G11B
27/10 (20060101); H04N 5/77 (20060101); H04N
5/232 (20060101); H04N 1/21 (20060101); H04N
5/92 (20060101); H04N 9/804 (20060101); H04N
5/355 (20110101); H04N 5/3745 (20110101); H04N
9/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
101064791 |
|
Oct 2007 |
|
CN |
|
101064792 |
|
Oct 2007 |
|
CN |
|
2003-125344 |
|
Apr 2003 |
|
JP |
|
2013172210 |
|
Sep 2013 |
|
JP |
|
2014-048459 |
|
Mar 2014 |
|
JP |
|
Other References
Notification of the First Office Action issued by the China
National Intellectual Property Administration on Jul. 16, 2019 in
corresponding Chinese Patent Application No. 201610815188.4, with
English translation. cited by applicant.
|
Primary Examiner: Hannett; James M
Attorney, Agent or Firm: Carter, DeLuca & Farrell
LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser.
No. 15/258,564, filed on Sep. 7, 2016, which claims the benefit of
and priority to Japanese Patent Application Nos. 2015-177587 and
2016-124714, filed on Sep. 9, 2015 and Jun. 23, 2016, respectively,
the entire contents of each of which are hereby incorporated by
reference herein in their entireties.
Claims
What is claimed is:
1. A playback device comprising: one or more processors; and a
memory including instructions stored thereon that, when executed by
the one or more processors, cause the playback device to function
as: a playback unit that playbacks first image files which are
acquired based on a first signal charge generated during a first
accumulation time and second image files which are acquired based
on a second signal charge generated during a second accumulation
time and associated with the first image files, wherein the
playback unit playbacks the first image files at a start of
playbacking and playbacks the second image files when a pause
instruction is received, wherein the second accumulation time
overlaps with at least part of the first accumulation time, wherein
the playback unit playbacks the first image files and the second
image files acquired by an imaging device including a plurality of
pixels, each of the plurality of pixels including a first
transistor and a second transistor, and wherein the playback unit
acquires the first image files based on the first signal charge
output via the first transistor and the second image files based on
the second signal charge output via the second transistor.
2. The playback device according to claim 1, wherein the first
image files are still image data, and the second image files are
moving image data.
3. The playback device according to claim 1, wherein the second
accumulation time is relatively longer than the first accumulation
time, and the second image files are recorded in synch with the
first image files during a synchronization period including the
first accumulation time.
4. The playback device according to claim 1, wherein an exposure
condition for acquiring the first image files and an exposure
condition for acquiring the second image files are different from
each other.
5. The playback device according to claim 1, wherein the second
accumulation time is relatively longer than the first accumulation
time.
6. The playback device according to claim 1, wherein each of the
plurality of pixels including a first photoelectric conversion unit
corresponding to the first transistor and a second photoelectric
conversion unit corresponding to the second transistor, and wherein
the playback unit acquires the first image files based on the first
signal charge generated by the first photoelectric conversion unit
and the second image files based on the second signal charge
generated by the second photoelectric conversion unit.
7. The playback device according to claim 1, wherein each of the
plurality of pixels including one photoelectric conversion unit, a
first signal holding unit corresponding to the first transistor and
a second signal holding unit corresponding to the second
transistor, and wherein the playback unit acquires the first image
files based on signals generated by transferring a signal charge,
generated by the photoelectric conversion unit during one shooting
period, to the first signal holding unit at least once, and the
second image files based on signals generated by transferring a
signal charge, generated by the photoelectric conversion unit
during the one shooting period, to the second signal holding unit
at least twice or more and adding up the signal charges.
8. The playback device according to claim 1, wherein the first
image files and the second image files are stored in storage on a
network.
9. The playback device according to claim 1, wherein the first
image files and the second image files are associated to each other
with time codes therein.
10. The playback device according to claim 1, wherein the playback
unit switches between playbacking of the first image files and
playbacking of the second image files in accordance with a frame
rate.
11. The playback device according to claim 1, wherein the first
image files and the second image files are stored in one file
including synchronization information for synchronizing the first
image files and the second image files frame by frame.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an imaging device having an image
playback function, and a playback device.
Description of the Related Art
If a moving image and a still image can be shot at the same time
with one camera, not only can a shooting scene be viewed as a
moving image, but also a decisive scene in the moving image can be
seen as a still image for fun. This can significantly enhance the
values of shot images. Further, if a moving image at a normal frame
rate and a moving image at a high frame rate can be shot at the
same time with one camera, a specific scene can be switched to a
slow-motion moving image to enjoy the image as a high-definition
moving image. This can give a viewer an uplifting feeling.
In the meantime, when a phenomenon, so-called jerkiness, like a
kind of frame-by-frame advance happens to a moving image played
back, it is common that the quality of the moving image is largely
degraded. In order to suppress the jerkiness, there is a need to
set an accumulation time close to one frame period in a series of
shooting processes. In other words, if the frame rate is 30 fps, a
relatively longer accumulation time, such as 1/30 second or 1/60
second, will be adequate. Particularly, in such a situation that
the attitude of a camera is instable such as a helicopter shot,
this setting is important.
On the other hand, since a still image is required to have the
sharpness of shooting a moment, there is a need to set a short
accumulation time, for example, about 1/1000 second, in order to
obtain a stop motion effect. Further, in the case of a moving image
at a high frame rate, one frame period is short. Therefore, for
example, when the frame rate is 120 fps, a short accumulation time
such as 1/125 second or 1/250 second is inevitably set.
Shooting two images at the same time through a single photographic
lens, such as a moving image and a still image, or a moving image
at a normal frame rate and a moving image at a high frame rate,
means that the aperture values used to shooting these images are
the same. Even in this case, it is desired that similar levels of
signal charge should be obtained in an imaging element while
shooting two images in different accumulation time settings to
obtain noiseless images having excellent S/N ratios.
Japanese Patent Application Laid-Open No. 2014-048459 discloses an
imaging device including a pair of photodiodes having the shape of
pupils asymmetric with respect to each pixel. In the imaging device
described in Japanese Patent Application Laid-Open No. 2014-048459,
the light-receiving efficiency of one of the pair of photodiodes is
high and the light-receiving efficiency of the other photodiode is
low. Two signals from the pair of photodiodes are used as separate
pieces of image data so that the two images can be shot at the same
time.
Further, Japanese Patent Application Laid-Open No. 2003-125344
discloses an imaging device that shoots a high-resolution image (an
image having a quality enough for viewing as a still image) during
moving image shooting, and a method of processing the shot image.
Japanese Patent Application Laid-Open No. 2003-125344 teaches that
images are reproduced up to a predetermined resolution
(high-resolution images up to the same resolution as the moving
image) by a progressive method during moving image playback to
enable viewing as a moving image, while the high-resolution image
is extracted and transferred as a still image in the case of a
still image application.
Although such an imaging device capable of shooting two images at
the same time as described in Japanese Patent Application Laid-Open
No. 2014-048459 can be expected to improve convenience by
presenting two images properly, there is no specific mention on a
useful presentation method.
Further, Japanese Patent Application Laid-Open No. 2003-125344 does
not present a preferred playback mode of switching between the
moving image and the still image at arbitrary times.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an imaging
device capable of acquiring images suitable for viewing of both a
moving image and a still image, and a playback device capable of
presenting the acquired images properly.
According to one aspect of the present invention, there is provided
an imaging element that acquires a first image based on signal
charge generated during a first accumulation time, and a second
image based on signal charge generated during a second accumulation
time relatively longer than the first accumulation time and
recorded in synch with the first image during a synchronization
period including the first accumulation time, and a moving image
file generating unit that generates a moving image file including a
first moving image based on the first image, a second moving image
based on the second image, and synchronization information for
synchronizing the first moving image and the second moving image
frame by frame.
According to another aspect of the present invention, there is
provided a playback device including a playback unit that playbacks
a moving image file captured by an imaging device that acquires a
first image based on signal charge generated during a first
accumulation time, and a second image based on signal charge
generated during a second accumulation time relatively longer than
the first accumulation time and recorded in synch with the first
image during a synchronization period including the first
accumulation time, wherein the playback unit includes as modes of
playbacking the moving image file a first presentation mode without
any change in presented image with time, and a second presentation
mode to change the presented image with time, wherein a first
moving image based on the first image is selected from the moving
image file and presented in the first presentation mode, and a
second moving image based on the second image is selected from the
moving image file and presented in the second presentation
mode.
According to still another aspect of the present invention, there
is provided a playback method of playbacking a moving image file
shot with an imaging device that acquires a first image based on
signal charge generated during a first accumulation time, and a
second image based on signal charge generated during a second
accumulation time relatively longer than the first accumulation
time and recorded in synch with the first image during a
synchronization period including the first accumulation time, the
method including selecting and presenting a first moving image
based on the first image from the moving image file according to a
playback instruction in a first presentation mode without any
change in presented image with time, and selecting and presenting a
second moving image based on the second image from the moving image
file according to a playback instruction in a second presentation
mode to change the presented image with time.
Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference
to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A and FIG. 1B are external views of an imaging device
according to a first embodiment of the present invention.
FIG. 2 is a block diagram illustrating a schematic configuration of
the imaging device according to the first embodiment of the present
invention.
FIG. 3 is a block diagram illustrating a configuration example of
an imaging element of the imaging device according to the first
embodiment of the present invention.
FIG. 4 is a cross-sectional view illustrating the internal
structure of the imaging element in the imaging device according to
the first embodiment of the present invention.
FIG. 5 is a graph illustrating a relationship between the angle of
a light beam incident on a pixel and output from photodiodes.
FIG. 6A and FIG. 6B are diagrams illustrating the relationship
between a photographing optical system and the imaging element in
the imaging device according to the first embodiment of the present
invention.
FIG. 7A, FIG. 7B, and FIG. 7C are schematic diagrams for describing
image signals output from the imaging element.
FIG. 8 is a circuit diagram illustrating a configuration example of
each pixel of the imaging element of the imaging device according
to the first embodiment of the present invention.
FIG. 9 and FIG. 10 are planar layout diagrams illustrating the main
part of each pixel of the imaging element of the imaging device
according to the first embodiment of the present invention.
FIG. 11 is a circuit diagram illustrating a configuration example
of readout circuits of the imaging element of the imaging device
according to the first embodiment of the present invention.
FIG. 12 is a timing chart illustrating a driving sequence of the
imaging element.
FIG. 13 is a graph illustrating temporal changes in signal charge
in photodiodes.
FIG. 14A, FIG. 14B, and FIG. 14C are potential diagrams of the
pixel taken along A-B line in FIG. 9.
FIG. 15 is a cross-sectional view illustrating the propagation of
light and the behavior of electric charges generated by the
photoelectric conversion inside the imaging element.
FIG. 16 is a timing chart for describing an imaging sequence in the
imaging device according to the first embodiment of the present
invention.
FIG. 17 is a diagram illustrating an example of time code values
added to each frame of moving image data.
FIG. 18 is a diagram illustrating an example of the file structure
of "picture A" and "picture B."
FIG. 19 is a diagram for describing a shooting condition setting
screen for "picture A" and "picture B."
FIG. 20 is a diagram illustrating a relationship between ISO
sensitivity ranges of "picture A" and "picture B."
FIG. 21 is a program AE chart in a dual image mode of the imaging
device according to the first embodiment of the present
invention.
FIG. 22 is a chart for describing a shutter speed difference
between "picture A" and "picture B" along an imaging sequence.
FIG. 23 is a diagram illustrating a state of a display unit during
live view display after the imaging device is powered up.
FIG. 24A and FIG. 24B are diagrams illustrating one frame among
image frames acquired by operating a switch ST and a switch MV.
FIG. 25 is a flowchart illustrating a series of processing
procedure steps including crosstalk correction.
FIG. 26 is a diagram for describing crosstalk correction processing
performed in a digital signal processing unit.
FIG. 27 is a graph illustrating a specific example of crosstalk
correction functions.
FIG. 28 is a diagram illustrating an example of an image after
being subjected to crosstalk correction.
FIG. 29 is a diagram illustrating a state of displaying "picture A"
and "picture B" next to each other on a display unit.
FIG. 30 is a diagram for describing an image playback method
according to the first embodiment of the present invention.
FIG. 31A, FIG. 31B, FIG. 31C, FIG. 31D, and FIG. 31E are diagrams
for describing file formats for storing "picture A" and "picture
B."
FIG. 32 is a circuit diagram illustrating a configuration example
of pixels of an imaging element of the imaging device according to
a third embodiment of the present invention.
FIG. 33 is a program AE chart in a dual image mode of the imaging
device according to the third embodiment of the present
invention.
FIG. 34 is a flowchart illustrating a method of driving the imaging
device according to the third embodiment of the present
invention.
FIG. 35 is a chart for describing a method of driving the imaging
element in a first moving image/still image shooting mode.
FIG. 36 is a timing chart illustrating a driving sequence of the
imaging element in the first moving image/still image shooting
mode.
FIG. 37 is a chart for describing a method of driving the imaging
element in a second moving image/still image shooting mode.
FIG. 38 is a timing chart illustrating a driving sequence of the
imaging element in the second moving image/still image shooting
mode.
DESCRIPTION OF THE EMBODIMENTS
Preferred embodiments of the present invention will now be
described in detail in accordance with the accompanying
drawings.
First Embodiment
An imaging device according to a first embodiment of the present
invention will be described with reference to FIG. 1A to FIG. 30.
In the present embodiment, description will be made by taking, as
an example of a preferred embodiment of the present invention, an
imaging device including an imaging element, a photographing
optical system, and the like for imaging, and an image playback
device. Note that the image playback device is not necessarily
required to be part of the imaging device, and it may be configured
in hardware different from that of the imaging element and the
photographing optical system. Further, the overall or part of the
function of the image playback device may be included in the
imaging element.
FIG. 1A and FIG. 1B are external views of a digital still motion
camera as an example of the imaging device according to the present
embodiment. FIG. 1A illustrates a front view and FIG. 1B
illustrates a back view.
An imaging device 100 according to the present embodiment includes
a housing 151, a photographing optical system 152 provided in a
front portion of the housing 151, and a switch ST 154 and a
propeller 162 provided on the top face of the housing 151. The
imaging device 100 also includes, on the back side of the housing
151, a display unit 153, a switch MV 155, a shooting mode selecting
lever 156, a menu button 157, up and down switches 158, 159, a dial
160, and a playback button 161.
The housing 151 is a case for housing various functional parts,
such as the imaging element, a shutter, and the like, which
constitute the imaging device 100. The photographing optical system
152 is an optical system for forming an optical image of an object.
The display unit 153 is configured to include a display for
displaying photographic information and an image. A movable
mechanism may be provided in the display unit 153 to angle a screen
as necessary. The display unit 153 has a display brightness range
capable of displaying an image having a wide dynamic range without
suppressing the brightness range of the image. The switch ST 154 is
a shutter button mainly used to shoot a still image. The switch MV
155 is a button used to start or stop moving image shooting. The
shooting mode selecting lever 156 is a selector switch for
selecting a shooting mode. The menu button 157 is a button to move
to a function setting mode for setting the function of the imaging
device 100. The up and down switches 158, 159 are buttons used to
change various set values. The dial 160 is a dial for changing
various set values. The playback button 161 is a button to move to
a playback mode for playbacking, on the display unit 153, an image
recorded on a recording medium housed in the imaging device 100.
The propeller 162 is to make the imaging device 100 float in the
air in order to take images from the air.
FIG. 2 is a block diagram illustrating a schematic configuration of
the imaging device 100 according to the present embodiment. As
illustrated in FIG. 2, the imaging device 100 includes an aperture
181, an aperture control unit 182, an optical filter 183, an
imaging element 184, analog front ends 185, 186, digital signal
processing units 187, 188, and a timing generation unit 189. The
imaging device 100 also includes a system control CPU 178, a switch
input unit 179, an image memory 190, and a flight controller 200.
Further, the imaging device 100 includes a display interface unit
191, a recording interface unit 192, a recording medium 193, a
print interface unit 194, an external interface unit 196, and a
radio interface unit 198.
The imaging element 184 is to convert an optical image of an object
formed through the photographing optical system 152 into an
electrical image signal. Though not particularly limited, the
imaging element 184 includes the number of pixels, the signal
readout rate, the color gamut, and the dynamic range enough to meet
a standard such as the UHDTV (Ultra High Definition Television)
standard. The aperture 181 is to adjust the amount of light passing
through the photographing optical system 152. The aperture control
unit 182 is a circuit or a processor configured to control the
aperture 181. The optical filter 183 is to limit the wavelength of
light incident on the imaging element 184 and the spatial frequency
to be transmitted to the imaging element 184. The photographing
optical system 152, the aperture 181, the optical filter 183, and
the imaging element 184 are disposed on an optical axis 180 of the
photographing optical system 152.
The analog front ends 185, 186 are a circuit or a processor
configured to perform analog signal processing and analog-digital
conversion processing of an image signal output from the imaging
element 184. Each of the analog front ends 185, 186 is, for
example, composed of a correlated double sampling (CDS) circuit for
removing noise, an amplifier for adjusting signal gain, an A/D
converter for converting an analog signal to a digital signal, and
the like. The digital signal processing units 187, 188 are to
compress image data after making various corrections to digital
image data output from the analog front ends 185, 186. The
corrections made by the digital signal processing units 187, 188
include crosstalk correction to be described later. The timing
generation unit 189 is a circuit or a processor configured to
output various timing signals to the imaging element 184, the
analog front ends 185, 186, and the digital signal processing units
187, 188. The system control CPU 178 is a control unit for carrying
out various operations and performing overall control of the
imaging device 100. The image memory 190 is to temporarily store
image data.
The display interface unit 191 is an interface between the system
control CPU 178 and the display unit 153 to display a shot image in
the display unit 153. The recording medium 193 is a recording
medium such as a semiconductor memory to record image data,
additional data, and the like, which may be equipped in the imaging
device 100 or be removable. The recording interface unit 192 is an
interface between the system control CPU 178 and the recording
medium 193 to perform recording on the recording medium 193 or
reading from the recording medium 193. The external interface unit
196 is an interface between the system control CPU 178 and an
external device to communicate with the external device such as an
external computer 197. The print interface unit 194 is an interface
between the system control CPU 178 and a printer 195 to output a
shot image to the printer 195 such as a small ink-jet printer in
order to print out the shot image. The radio interface unit 198 is
an interface between the system control CPU 178 and a network 199
such as the Internet to communicate with the network 199. The
switch input unit 179 includes plural switches to switch various
modes, such as the switch ST 154 and the switch MV 155. The flight
controller 200 is a controller to control the propeller 162 so as
to fly the imaging device 100 in order to do shooting from the
air.
In an imaging device including an image playback device like the
imaging device 100 described in the present embodiment, shot image
data can be playbacked using the display unit 153 or an external
monitor. During the playback of the image data, the image data and
additional data are read out from the recording medium 193. The
readout data are demodulated in the digital signal processing units
187, 188 according to an instruction from the system control CPU
178 to be presented as an image in the display unit 153 through the
display interface unit 191. A user can operate an operation part
(the menu button 157, the up and down switches 158, 159, the dial
160, and the like) provided on the back side of the imaging device
100 to control the operation during playback. The user operations
include the playback, stop, and pause of a moving image.
FIG. 3 is a block diagram illustrating a configuration example of
the imaging element 184. As illustrated in FIG. 3, the imaging
element 184 includes a pixel array 302, a vertical scanning circuit
307, readout circuits 308A, 308B, and timing control circuits 309A,
309B.
In the pixel array 302, a plurality of pixels 303 are arranged in
the shape of a matrix. Although the actual number of pixels 303
belonging to the pixel array 302 is generally enormous, only 16
pixels 303 arranged in a 4.times.4 matrix are illustrated here for
the sake of simplifying the figure. Each of the plurality of pixels
303 includes a pair of a pixel element 303A and a pixel element
303B. In FIG. 3, the upper half area of the pixel 303 is the pixel
element 303A, and the lower half area of the pixel 303 is the pixel
element 303B. The pixel element 303A and the pixel element 303B
generate signals by photoelectric conversion, respectively.
Signal output lines 304A, 304B extending in the column direction
are provided in each column of the pixel array 302, respectively.
The signal output line 304A in each column is connected to the
pixel elements 303A belonging to the column. Signals from the pixel
elements 303A are output to the signal output line 304A. The signal
output line 304B in each column is connected to the pixel elements
303B belonging to the column. Signals from the pixel elements 303B
are output to the signal output line 304B. Further, in each column
of the pixel array 302, a power source line 305 and a ground line
306 extending in the column direction are provided, respectively.
The power source line 305 and the ground line 306 in each column
are connected to the pixels 303 belonging to the column. The power
source line 305 and the ground line 306 may also be signal lines
extending in the row direction.
The vertical scanning circuit 307 is arranged adjacent to the pixel
array 302 in the row direction. The vertical scanning circuit 307
outputs predetermined control signals to the plurality of pixels
303 of the pixel array 302 in units of rows through unillustrated
control lines arranged to extend in the row direction in order to
control readout circuits in the pixels 303. In FIG. 3, a reset
pulse .phi.RESn and transfer pulses .phi.TXnA, .phi.TXnB are
illustrated as control signals (where n is an integer corresponding
to each row number).
The readout circuits 308A, 308B are arranged adjacent to the pixel
array 302 in the column direction to sandwich the pixel array 302
therebetween. The readout circuit 308A is connected to the signal
output line 304A in each column. The readout circuit 308A
selectively activates the signal output line 304A in each column
sequentially to read signals from the signal output line 304A in
each column in a sequential order and perform predetermined signal
processing. Similarly, the readout circuit 308B is connected to the
signal output line 304B in each column. The readout circuit 308B
selectively activates the signal output line 304B in each column
sequentially to read signals from the signal output line 304B in
each column in a sequential order and perform predetermined signal
processing. Each of the readout circuits 308A, 308B can include a
noise cancellation circuit, an amplifier circuit, an analog/digital
converter circuit, and a horizontal scanning circuit, respectively,
to output signals after being subjected to the predetermined signal
processing sequentially.
The timing control circuit 309A is connected to the vertical
scanning circuit 307 and the readout circuit 308A. The timing
control circuit 309A outputs a control signal to control the drive
timing of the vertical scanning circuit 307 and the readout circuit
308A. The timing control circuit 309B is connected to the vertical
scanning circuit 307 and the readout circuit 308B. The timing
control circuit 309B outputs a control signal to control the drive
timing of the vertical scanning circuit 307 and the readout circuit
308B.
FIG. 4 is a cross-sectional view illustrating the internal
structure of each pixel 303 of the imaging element 184. As
illustrated in FIG. 4, each pixel 303 includes two photodiodes
310A, 310B, a light guide 255, and a color filter 256. The
photodiode 310A forms part of the pixel element 303A and the
photodiode 310B forms part of the pixel element 303B. The
photodiodes 310A, 310B are provided in a silicon substrate 251. The
light guide 255 is provided in an insulating layer 254 provided
over the silicon substrate 251. The insulating layer 254 is, for
example, made of silicon oxide, and the light guide 255 is made of
a material having a higher refractive index than the insulating
layer 254 such as silicon nitride. Interconnection layers 252 are
provided in the insulating layer 254 between adjacent light guides
255. The color filter 256 having predetermined spectral
transmittance characteristics is provided over the light guide 255.
Note that FIG. 4 illustrates an example in which color filters of
adjacent two pixels 303 are color filters 256, 257 having spectral
transmittance characteristics different from each other.
The light guide 255 has the property of confining light therein due
to a refractive index difference from the insulating layer 254.
This enables the light guide 255 to guide light incident through
the color filter 256 to the photodiodes 310A, 310B. The photodiodes
310A, 310B are arranged asymmetric with respect to the light guide
255, and a light flux propagating through the light guide 255
enters the photodiode 310A with relatively high efficiency and
enters the photodiode 310B with relatively low efficiency. Further,
the depth and inclined angle of the light guide 255 can be adjusted
to prevent nonuniformity in the incident angle characteristics of
incident light flux capable of being converted photoelectrically by
the photodiodes 310A, 310B effectively.
FIG. 5 is a graph illustrating a relationship between the angle of
a light beam incident on a pixel and output from photodiodes. In
FIG. 5, the abscissa represents the angle of the light beam
incident on the pixel, and the ordinate represents output from the
photodiodes. In FIG. 5, an output characteristic 261 from the
photodiode 310A and an output characteristic 262 from the
photodiode 310B are illustrated.
As illustrated in FIG. 5, the characteristic 261 and the
characteristic 262 both exhibit gentle hill-like shapes symmetric
about peaks, each of which the incident angle of the light beam is
zero. The peak intensity PB of the characteristic 262 is about 1/8
of the peak intensity PA of the characteristic 261. This means that
the dependences of the photodiodes 310A, 310B on the incident angle
are both small and the light-receiving efficiency of the photodiode
310B is 1/8 of that of the photodiode 310A. In other words, when
the sensitivity of the photodiode 310B is replaced by a set value
of the ISO sensitivity, the sensitivity of the photodiode 310B
becomes lower by three steps than that of the photodiode 310A.
Next, a relationship between the photographing optical system 152
and the imaging element 184 will be described more specifically
with reference to FIG. 6A and FIG. 6B. FIG. 6A and FIG. 6B are
diagrams for describing the relationship between the photographing
optical system 152 and the imaging element 184. FIG. 6A is a
diagram when the photographing optical system 152 is viewed from a
direction along an optical axis 180. FIG. 6B is a diagram more
specifically illustrating a section from the photographing optical
system 152 to the imaging element 184 in FIG. 2.
As illustrated in FIG. 6B, it is assumed that the imaging element
184 includes a pixel 276 located in a central portion of the
imaging area and a pixel 277 located near the outer edge of the
imaging area. In this case, the pixel 276 can receive a light flux
from an area surrounded by a light beam 272 and a light beam 273.
The pixel 277 can receive a light flux from an area surrounded by a
light beam 274 and a light beam 275. On this occasion, since a
field lens 270 is arranged between the optical filter 183 and the
photographing optical system 152, the light flux received by the
pixel 276 and the light flux received by the pixel 277 are
overlapped near the photographing optical system 152 as indicated
by an area 271 in FIG. 6A. As a result, both of the pixels can
receive the light flux emitted from the photographing optical
system 152 with high efficiency.
FIG. 7A to FIG. 7C are schematic diagrams for describing image
signals output from the imaging element. Suppose here that color
filters having predetermined optical transmittance characteristics
are arranged over the pixel array 302 in the layout of a color
filter array 281 illustrated in FIG. 7A. FIG. 7A schematically
illustrates the pixel array 302 with the pixels 303 arranged in a
matrix with six rows and eight columns, and the colors of color
filters arranged on respective pixels. In FIG. 7A, R denotes a red
color filter, G1 and G2 denote green color filters, and B denotes a
blue color filter, respectively. The illustrated color filter array
281 is a color filter array, a so-called Bayer array, where color
filters of respective colors are arranged repeatedly in each row
like G1BG1B . . . , RG2RG2 . . . , G1BG1B . . . , and so on.
Output data 282, 283 illustrated in FIG. 7B and FIG. 7C are
obtained from the pixel array 302 having such a color filter array
281. In FIG. 7B, g1A and g2A represent output from pixel elements
303A of the pixels 303 with the green color filters arranged
thereon. bA represents output from pixel elements 303A of the
pixels 303 with the blue color filter arranged thereon. rA
represents output from pixel elements 303A of the pixels 303 with
the red color filter arranged thereon. In FIG. 7C, g1B and g2B
represent output from pixel elements 303B of the pixels 303 with
the green color filters arranged thereon. bB represents output from
pixel elements 303B of the pixels 303 with the blue color filter
arranged thereon. rB represents output from pixel elements 303B of
the pixels 303 with the red color filter arranged thereon.
As described with reference to FIG. 3, two types of output from the
readout circuits 308A, 308B can be obtained from the imaging
element 184. One type of output is the output data 282 illustrated
in FIG. 7B, and the other type of output is the output data 283
illustrated in FIG. 7C. The output data 282 are subjected to
predetermined signal processing to generate an image signal
"picture A." The output data 283 are subjected to predetermined
signal processing to generate an image signal "picture B." In the
following description, the image signal based on the output data
282 is referred to as "picture A," and the image signal based on
the output data 283 is referred to as "picture B." Although the
"picture A" and "picture B" are image signals after being subjected
to a predetermined correction in a precise sense, image signals
before or during the correction may also be referred to as the
"picture A" and "picture B" for the purpose of illustration.
FIG. 8 is a circuit diagram illustrating a configuration example of
each pixel 303. As mentioned above, the pixel 303 includes the
pixel element 303A and the pixel element 303B. The pixel element
303A includes the photodiode 310A, a transfer transistor 311A, a
floating diffusion region 313A, a reset transistor 314A, and an
amplifier transistor 315A. The pixel element 303B includes the
photodiode 310B, a transfer transistor 311B, a floating diffusion
region 313B, a reset transistor 314B, and an amplifier transistor
315B. Note that the photodiode 310A corresponds to the photodiode
310A illustrated in FIG. 4, and the photodiode 310B corresponds to
the photodiode 310B illustrated in FIG. 4.
The anode of the photodiode 310A is connected to the ground line
306, and the cathode of the photodiode 310A is connected to the
source of the transfer transistor 311A. The drain of the transfer
transistor 311A is connected to the source of the reset transistor
314A and the gate of the amplifier transistor 315A. A connection
node of the drain of the transfer transistor 311A, the source of
the reset transistor 314A, and the gate of the amplifier transistor
315A forms the floating diffusion region 313A. The drain of the
reset transistor 314A and the drain of the amplifier transistor
315A are connected to the power source line 305. The source of the
amplifier transistor 315A that forms a pixel signal output part
316A is connected to the signal output line 304A.
Similarly, the anode of the photodiode 310B is connected to the
ground line 306, and the cathode of the photodiode 310B is
connected to the source of the transfer transistor 311B. The drain
of the transfer transistor 311B is connected to the source of the
reset transistor 314B and the gate of the amplifier transistor
315B. A connection node of the drain of the transfer transistor
311B, the source of the reset transistor 314B, and the gate of the
amplifier transistor 315B forms the floating diffusion region 313B.
The drain of the reset transistor 314B and the drain of the
amplifier transistor 315B are connected to the power source line
305. The source of the amplifier transistor 315B that forms a pixel
signal output part 316B is connected to the signal output line
304B.
The pixels 303 in each row are connected to a reset control line
319 and transfer control lines 320A, 320B arranged in the row
direction from the vertical scanning circuit 307. The reset control
line 319 is connected to the gate of the reset transistor 314A and
the gate of the reset transistor 314B. The transfer control line
320A is connected to the gate of the transfer transistor 311A via a
contact part 312A. The transfer control line 320B is connected to
the gate of the transfer transistor 311B via a contact part 312B.
The reset control line 319 supplies the reset pulse .phi.RESn,
output from the vertical scanning circuit 307, to the gate of the
reset transistor 314A and the gate of the reset transistor 314B.
The transfer control line 320A supplies the transfer pulse
.phi.TXnA, output from the vertical scanning circuit 307, to the
gate of the transfer transistor 311A. The transfer control line
320B supplies the transfer pulse .phi.TXnB, output from the
vertical scanning circuit 307, to the gate of the transfer
transistor 311B. Note that n attached to the reset pulse .phi.RESn,
the transfer pulse .phi.TXnA, and the transfer pulse .phi.TXnB is
an integer corresponding to the row number. In FIG. 8, n is
replaced by an integer corresponding to the row number.
The photodiode 310A is a first photoelectric conversion unit that
generates electric charge by photoelectric conversion, and the
photodiode 310B is a second photoelectric conversion unit that
generates electric charge by photoelectric conversion. The floating
diffusion regions 313A, 313B are regions to accumulate electric
charge. The transfer transistor 311A transfers, to the floating
diffusion region 313A, the electric charge generated by the
photodiode 310A. The transfer transistor 311B transfers, to the
floating diffusion region 313B, the electric charge generated by
the photodiode 310B.
When a high-level transfer pulse .phi.TXnA is output from the
vertical scanning circuit 307, the transfer transistor 311A is
turned on to connect the photodiode 310A and the floating diffusion
region 313A. Similarly, when a high-level transfer pulse .phi.TXnB
is output from the vertical scanning circuit 307, the transfer
transistor 311B is turned on to connect the photodiode 310B and the
floating diffusion region 313B. When a high-level reset pulse
.phi.RESn is output from the vertical scanning circuit 307, the
reset transistors 314A, 314B are turned on to reset the photodiodes
310A, 310B, and the floating diffusion regions 313A, 313B.
When a low-level transfer pulse .phi.TXnA is output from the
vertical scanning circuit 307, the transfer transistor 311A is
turned off to cause the photodiode 310A to start accumulating
signal charge generated by the photoelectric conversion. After
that, when the high-level transfer pulse .phi.TXnA is output from
the vertical scanning circuit 307, the transfer transistor 311A is
turned on to transfer the signal charge of the photodiode 310A to
the floating diffusion region 313A. Then, the amplifier transistor
315A amplifies and outputs, to the signal output line 304A, the
voltage of the floating diffusion region 313A according to the
amount of signal charge transferred from the photodiode 310A.
Similarly, when a low-level transfer pulse .phi.TXnB is output from
the vertical scanning circuit 307, the transfer transistor 311B is
turned off to cause the photodiode 310B to start accumulating
signal charge generated by the photoelectric conversion. After
that, when the high-level transfer pulse .phi.TXnB is output from
the vertical scanning circuit 307, the transfer transistor 311B is
turned on to transfer the signal charge of the photodiode 310B to
the floating diffusion region 313B. Then, the amplifier transistor
315B amplifies and outputs, to the signal output line 304B, the
voltage of the floating diffusion region 313B according to the
amount of signal charge transferred from the photodiode 310B.
FIG. 9 and FIG. 10 are planar layout diagrams illustrating the main
part of each pixel 303. Among the constituent elements of the pixel
303, the photodiodes 310A, 310B, the transfer transistors 311A,
311B, and the floating diffusion regions 313A, 313B are illustrated
in FIG. 9. The other circuit elements including the reset
transistors 314A, 314B and the amplifier transistors 315A, 315B are
represented as a readout circuit part 321 in FIG. 9 to omit
detailed illustration. Further, the signal output lines 304A, 304B,
and the power source line 305 arranged in the vertical direction of
the pixel 303 are omitted, and the contact parts of the reset
control line 319, the power source line 305, and the ground line
306 are omitted. In addition to the constituent elements
illustrated in FIG. 9, the light guide 255 described with reference
to FIG. 4 is illustrated in FIG. 10. In the light guide 255, the
shaded area indicates a low refractive index area and the outlined
blank area indicates a high refractive index area, namely a light
guiding area.
In FIG. 9 and FIG. 10, the contact part 312A is a contact part to
connect the transfer control line 320A and the gate of the transfer
transistor 311A. The contact part 312B is a contact part to connect
the transfer control line 320B and the gate of the transfer
transistor 311B. Each of the photodiodes 310A, 310B is a
photoelectric conversion unit that performs the photoelectric
conversion, having a first conductivity-type (e.g., p-type)
semiconductor region and a second conductivity-type (e.g., n-type)
semiconductor region (n-type electron accumulation region) to form
a p-n junction with the first conductivity-type semiconductor
region. The second conductivity-type semiconductor region of the
photodiode 310A and the second conductivity-type semiconductor
region of the photodiode 310B are isolated by an isolation part
322.
The transfer transistors 311A, 311B, the contact parts 312A, 312B,
and the transfer control lines 320A, 320B are arranged
line-symmetric or substantially line-symmetric to the isolation
part 322 between the photodiodes 310A, 310B, respectively. On the
other hand, the light guide 255 is arranged in a position deviated
from the isolation part 322 as illustrated in FIG. 10. In other
words, the photodiode 310A occupies most of the area of the bottom
of the light guide 255, whereas the photodiode 310B slightly
overlaps the bottom of the light guide 255. Therefore, the
light-receiving efficiency of the photodiode 310A is relatively
high, and the light-receiving efficiency of the photodiode 310B is
relatively low.
In the imaging element 184 according to the present embodiment, the
ratio of the light-receiving efficiency between the photodiodes
310A and 310B is set to about 8:1, i.e., the difference in
sensitivity is set to about three steps. Then, two images are shot
in the settings of different accumulation times to obtain nearly
equal signal charge in each pixel element. This can make both
images be noiseless images having excellent S/N ratios, or can
synthesize both images to obtain a high-definition HDR image. The
details will be described later.
FIG. 11 is a circuit diagram illustrating a configuration example
of the readout circuits 308A, 308B of the imaging element 184.
Assuming the readout circuit 308A, "A" is suffixed to some
constituent elements in FIG. 11. It should be understood that "B"
will be suffixed to corresponding constituent elements in the
readout circuit 308B.
As illustrated in FIG. 11, the readout circuit 308A includes a
clamp capacitor CO, a feedback capacitor Cf, an operational
amplifier 406, a reference voltage source 407, and a switch 423.
One input terminal of the operational amplifier 406 is connected to
the signal output line 304A via the clamp capacitor CO. The
feedback capacitor Cf and the switch 423 are connected in parallel
between the one input terminal and the output terminal of the
operational amplifier 406. The other input terminal of the
operational amplifier is connected to a reference voltage source
407. The reference voltage source 407 supplies a reference voltage
Vref to the operational amplifier 406. The switch 423 is a switch
controlled by a signal PCOR to be turned on when the signal PCOR is
at high level so as to short-circuit both ends of the feedback
capacitor Cf.
The readout circuit 308A also includes switches 414, 415, 418, and
419, a capacitor CTSA, a capacitor CTNA, horizontal output lines
424, 425, and an output amplifier 421. The switches 414, 415 are
switches that control the writing of pixel signals to the
capacitors CTSA and CTNA. The switch 414 is a switch controlled by
a signal PTSA to be turned on when the signal PTSA is at high level
so as to connect the output terminal of the operational amplifier
406 and the capacitor CTSA. The switch 415 is a switch controlled
by a signal PTNA to be turned on when the signal PTNA is at high
level so as to connect the output terminal of the operational
amplifier 406 and the capacitor CTNA.
The switches 418, 419 are switches to control the output of pixel
signals, held in the capacitors CTSA and CTNA, to the output
amplifier 421. The switches 418, 419 are turned on in response to a
control signal from a horizontal shift register. Thus, the signal
written in the capacitor CTSA is output to the output amplifier 421
via the switch 418 and a horizontal output line 424. The signal
written in the capacitor CTNA is output to the output amplifier 421
via the switch 419 and a horizontal output line 425. The signal
PCOR, the signal PTNA, and the signal PTSA are signals supplied
from the timing generation unit 189 under the control of the system
control CPU 178.
The readout circuit 308B also have a configuration equivalent to
that of the readout circuit 308A. Note that a signal PTNB and a
signal PTSB in the following description are signals supplied from
the timing generation unit 189 under the control of the system
control CPU 178, having roles equivalent to the signal PTNA and the
signal PTSA in the readout circuit 308A.
Next, reset, accumulation, and readout operations in the imaging
element 184 will be sequentially described with reference to a
timing chart of FIG. 12 by taking, as an example, reading operation
from pixels 303 in the first row.
First, at time t1, the vertical scanning circuit 307 shifts the
transfer pulses .phi.TX1A, TX1B output to the transfer control
lines 320A, 320B from the low level to the high level. Thus, the
transfer transistors 311A, 311B are turned on. At this time, since
the high-level reset pulse .phi.RES1 is output to the reset control
line 319 from the vertical scanning circuit 307, the reset
transistors 314A, 314B are also in the on-state. Therefore, the
photodiodes 310A, 310B are connected to the power source line 305
via the transfer transistors 311A, 311B and the reset transistors
314A, 314B to get into the reset state. On this occasion, the
floating diffusion regions 313A, 313B are also in the reset
state.
Then, at time t2, the vertical scanning circuit 307 shifts the
transfer pulse .phi.TX1B from the high level to the low level.
Thus, the transfer transistor 311B is turned off to cause the
photodiode 310B to start accumulating signal charge by the
photoelectric conversion.
Then, at time t3, the vertical scanning circuit 307 shifts the
transfer pulse .phi.TX1A from the high level to the low level.
Thus, the transfer transistor 311A is turned off to cause the
photodiode 310A to start accumulating signal charge by the
photoelectric conversion.
Then, at time t4, the vertical scanning circuit 307 shifts the
reset pulse .phi.RES1 from the high level to the low level. Thus,
the reset transistors 314A, 314B are turned off to release the rest
of the floating diffusion regions 313A, 313B.
Accordingly, the potential of the floating diffusion region 313A is
read out as a pixel signal of a reset signal level to the signal
output line 304A via the amplifier transistor 315A, and input to
the readout circuit 308A. Further, the potential of the floating
diffusion region 313B is read out as a pixel signal of a reset
signal level to the signal output line 304B via the amplifier
transistor 315B, and input to the readout circuit 308B.
At time t4, since the high-level signal PCOR is output from the
timing generation unit 189 to the readout circuit 308A and the
readout circuit 308B, the switch 423 is in the on-state. Therefore,
the pixel signal of the reset signal level from the pixel element
303A is input to the readout circuit 308A in a state where the
operational amplifier 406 buffers the output of the reference
voltage Vref. Though not illustrated, the pixel signal of the reset
signal level from the pixel element 303B is also input to the
readout circuit 308B in the same manner.
Then, at time t5, the signal PCOR output from the timing generation
unit 189 to the readout circuit 308A and the readout circuit 308B
is changed from the high level to the low level to turn off the
switch 423.
Then, at time t6, the signal PTNA output from the timing generation
unit 189 to the readout circuit 308A is changed from the low level
to the high level to turn on the switch 415 so that the output of
the operational amplifier 406 at the time will be written to the
capacitor CTNA. Similarly, the signal PTNB output from the timing
generation unit 189 to the readout circuit 308B is changed from the
low level to the high level to turn on the switch 415 so that the
output of the operational amplifier 406 at the time will be written
to the capacitor CTNB.
Then, at time t7, the signal PTNA output from the timing generation
unit 189 to the readout circuit 308A is changed from the high level
to the low level to turn off the switch 415 so as to complete the
writing to the capacitor CTNA. Similarly, the signal PTNB output
from the timing generation unit 189 to the readout circuit 308B is
changed from the high level to the low level to turn off the switch
415 so as to complete the writing to the capacitor CTNB.
Then, at time t8, the vertical scanning circuit 307 changes the
transfer pulses .phi.TX1A, .phi.TX1B from the low level to the high
level to turn on the transfer transistors 311A, 311B. Thus, the
signal charge accumulated in the photodiode 310A is transferred to
the floating diffusion region 313A, and the signal charge
accumulated in the photodiode 310B is transferred to the floating
diffusion 31B.
Since the end timings of the accumulation periods of the
photodiodes 310A, 310B are synchronized by changing the transfer
pulses .phi.TX1A, .phi.TX1B to the high level at time t8 at the
same time, readout is done at the same time after both complete the
accumulation. Therefore, a crosstalk correction such as to correct
data on "picture B" using data on "picture A" or to correct data on
"picture A" using data on "picture B" can be made with a very
simple arithmetical operation.
Then, at time t9, the vertical scanning circuit 307 changes the
transfer pulses .phi.TX1A, .phi.TX1B from the high level to the low
level to turn off the transfer transistors 311A, 311B. Thus, the
readout of the signal charge accumulated in the photodiode 310A
into the floating diffusion region 313A and the readout of the
signal charge accumulated in the photodiode 310B into the floating
diffusion region 313B are completed.
Accordingly, the potential of the floating diffusion region 313A,
which is changed by the signal charge, is read out as a pixel
signal of an optical signal level to the signal output line 304A
via the amplifier transistor 315A, and input to the readout circuit
308A. Further, the potential of the floating diffusion region 313B,
which is changed by the signal charge, is read out as a pixel
signal of an optical signal level to the signal output line 304B
via the amplifier transistor 315B, and input to the readout circuit
308B.
Then, in the readout circuit 308A, voltage which is subjected to
inverted gain with respect to a voltage change at a capacitance
ratio between the clamp capacitor CO and the feedback capacitor Cf
is output from the operational amplifier 406. Similarly, in the
readout circuit 308B, voltage which is subjected to inverted gain
with respect to the voltage change at the capacitance ratio between
the clamp capacitor CO and the feedback capacitor Cf is output from
the operational amplifier 406.
Then, at time t10, the signal PTSA output from the timing
generation unit 189 to the readout circuit 308A is changed from the
low level to the high level to turn on the switch 414 so that the
output of the operational amplifier 406 at the time will be written
to the capacitor CTSA. Similarly, the signal PTSB output from the
timing generation unit 189 to the readout circuit 308B is changed
from the low level the high level to turn on the switch 414 so that
the output of the operational amplifier 406 at the time will be
written to the capacitor CTSB.
Then, at time t11, the signal PTSA output from the timing
generation unit 189 to the readout circuit 308A is changed from the
high level to the low level to turn off the switch 414 so as to
complete the writing to the capacitor CTSA. Similarly, the signal
PTSB output from the timing generation unit 189 to the readout
circuit 308B is changed from the high level to the low level to
turn off the switch 414 so as to complete the writing to the
capacitor CTSB.
Then, at time t12, the vertical scanning circuit 307 changes the
reset pulse .phi.RES1 from the low level to the high level to turn
on the reset transistors 314A, 314B. Thus, the floating diffusion
regions 313A, 313B are connected to the power source line 305 via
the reset transistors 314A, 314B to get into the reset state.
FIG. 13 is a graph illustrating temporal changes in signal charge
generated by photoelectric conversion and accumulated in the
photodiodes 310A, 310B. In FIG. 13, the abscissa of the graph
represents time and the ordinate represents the amount of signal
charge. On the time axis, time t1 to time t12 illustrated in FIG.
12 are marked.
At time t2, when the transfer pulse .phi.TX1B is changed to the low
level to turn off the transfer transistor 311B so as to start the
accumulation of signal charge in the photodiode 310B, the amount of
signal charge held in the photodiode 310B increases with time. The
increase in signal charge continues until the transfer pulse
.phi.TX1B is changed to the high level at time t8 to turn on the
transfer transistor 311B so as to transfer the signal charge of the
photodiode 310B to the floating diffusion region 313B.
Further, at time t3, the transfer pulse .phi.TX1A is changed to the
low level to turn off the transfer transistor 311A so as to start
the accumulation of signal charge in the photodiode 310A. Thus, the
amount of signal charge held in the photodiode 310A increases with
time. The increase in signal charge continues until the transfer
pulse .phi.TX1A is changed to the high level at time t8 to turn on
the transfer transistor 311A so as to transfer the signal charge of
the photodiode 310A to the floating diffusion region 313A.
At time t8, a signal charge amount LB held in the photodiode 310B
and a signal charge amount LA held in the photodiode 310A become
substantially the same level by cancelling out the difference in
light-receiving efficiency with the difference in accumulation
time.
In a period TM1 where the transfer pulse .phi.TX1B and the transfer
pulse .phi.TX1A are both at the low level, crosstalk occurs between
the photodiode 310A and the photodiode 310B. The period TM1 takes a
value shorter between the accumulation period of the photodiode
310A and the accumulation time of the photodiode 310B. Since the
crosstalk amount is approximately proportional to the amount of
signal charge, relatively more crosstalk occurs in a period TM2 as
the second half of the period TM1, where the signal charge amount
increases.
A crosstalk amount CTAB from the photodiode 310A to the photodiode
310B is proportional to the area of a region 953 indicated by
hatching diagonally right down. A crosstalk amount CTBA from the
photodiode 310B to the photodiode 310A is proportional to the area
of a region 954 indicated by hatching diagonally left down. If
these constants of proportion are defined by k and g, respectively,
the crosstalk amounts CTAB and CTBA can be expressed as follows.
CTAB=k.times.(LA.times.TM1)/2 (1) CTBA=g.times.(LA+LBS).times.TM1/2
(2)
LBS is a signal charge amount of the photodiode 310B at time t3.
Further, though not illustrated in FIG. 13, an approximation to
LB=LBS can be achieved if a period from time t2 to time t3 is
sufficiently shorter than the period TM1. Therefore, Equation (2)
can be modified as follows. CTBA=g.times.LB.times.TM1 (3)
Thus, it is found from Equation (1) and Equation (3) that the
crosstalk amount CTAB is a function of the signal charge amount LA
and a value (period TM1) shorter between the accumulation time of
the photodiode 310A and the accumulation time of the photodiode
310B. It is also found that the crosstalk amount CTBA is a function
of the signal charge amount LB and a value (period TM1) shorter
between the accumulation time of the photodiode 310A and the
accumulation time of the photodiode 310B.
FIG. 14A to FIG. 14C are potential diagrams of the pixel 303 taken
along A-B line in FIG. 9. FIG. 14A is a potential diagram at time
ta in FIG. 12, FIG. 14B is a potential diagram at time tb in FIG.
12, and FIG. 14C is a potential diagram at time tc in FIG. 12.
As illustrated in FIG. 14A, the transfer transistors 311A, 311B are
in the off-state at time ta, and signal charges at signal
accumulation levels 323A, 323B are accumulated in the photodiodes
310A, 310B, respectively. As mentioned above, although the
photodiode 310A and the photodiode 310B are different in
light-receiving efficiency, the signal accumulation levels 323A,
323B are substantially the same level by cancelling out the
difference in light-receiving efficiency with the difference in
accumulation time. Since this state lasts a relatively long time, a
phenomenon that the accumulated electric charge of the photodiode
310A leaks into the adjacent photodiode 310B and a phenomenon that
the accumulated electric charge of the photodiode 310B leaks into
the adjacent photodiode 310A occur at a non-negligible level.
As illustrated in FIG. 14B, the transfer transistors 311A, 311B are
in the on-state at time tb, and the potential barriers of the
transfer transistors 311A, 311B are low. Thus, the signal charge
accumulated in the photodiode 310A is transferred to the floating
diffusion region 313A, and the signal charge accumulated in the
photodiode 310B is transferred to the floating diffusion region
313B. On this occasion, although the potential barrier of the
isolation part 322 is also low, the potential barriers of the
transfer transistors 311A, 311B are sufficiently low. Therefore,
the phenomena that the accumulated electric charges of the
photodiodes 310A, 310B leak into the adjacent photodiodes 310B,
310A through the isolation part 322 at this timing hardly
occur.
As illustrated in FIG. 14C, the transfer transistors 311A, 311B are
in the off-state at time tc, and the potentials return to the state
in FIG. 14A.
FIG. 15 is a cross-sectional view illustrating the behavior of
electric charges generated by the propagation of light and
photoelectric conversion inside the imaging element 184. In FIG.
15, an arrow 451 indicates a light flux entering the pixel 303. The
light flux 451 first enters the color filter 256, where a
predetermined wavelength component is absorbed, passes through an
interfacial passivation film (not illustrated) corresponding to the
uppermost part of the insulating layer 254, and enters the light
guide 255. As described above with reference to FIG. 5, orientation
information of the light beam, i.e., pupil information is lost
inside the light guide 255 by the behavior of light waves. The
light flux 451 moves on the side of the silicon substrate 251 while
being confined in the light guide 255 due to the refractive index
difference between the light guide 255 and the insulating layer
254, and reaches the bottom of the light guide 255. The bottom of
the light guide 255 lies adjacent to the silicon substrate 251, and
the light flux emitted from the light guide 255 enters the silicon
substrate 251. The photodiode 310A and the photodiode 310B provided
adjacent to each other inside the silicon substrate 251 are
arranged to be greatly eccentric from the light guide 255.
Therefore, a light flux 452 as most of the light flux emitted from
the light guide 255 enters the photodiode 310A, and a light flux
453 as part of the rest of the light flux emitted from the light
guide 255 enters the photodiode 310B. The incident photons are
converted to signal charges in the photodiodes 310A, 310B.
On this occasion, signal charges generated inside the silicon
substrate 251 of the imaging element 184 may leak into adjacent
pixel elements by diffusion. For example, signal charge 454
generated in the photodiode 310A leaks into the photodiode 310B by
diffusion. Further, signal charge 455 generated in the photodiode
310B leaks into the photodiode 310A by diffusion. This phenomenon
has an adverse effect on the image, resulting in a blur in the
image.
FIG. 16 is a timing chart for describing an imaging sequence in the
imaging device according to the present embodiment. The term "time
code" on the top of the chart indicates time after power
activation, and "00:00:00:00" indicates "Hr:Min:Sec:Frame."
Time t31 is the power activation time of the imaging device
100.
At time t32, the switch MV 155 as a moving image shooting button is
operated by a user to be turned on to start imaging of "picture B"
and imaging of "picture A" are started in response thereto. In
response to operating the switch MV 155 as the button to shoot a
moving image, image data on the "picture B" are written onto the
recording medium 193 after being subjected to predetermined signal
processing.
The reason for imaging the "picture A" simultaneously with imaging
the "picture B" is to active a crosstalk correction to be described
later at all times. Since the transfer transistor 311A will be in
the on-state unless the transfer pulse .phi.TX1A illustrated in
FIG. 13 is at the low level, the signal charge generated in the
photodiode 310A is never accumulated. However, if only the period
of operating the switch ST 154 is targeted for the crosstalk
correction, the "picture B" recorded at the operating timing of the
switch ST 154 will be subjected to delicate brightness variation or
hue variation due to the influence of a crosstalk correction
error.
During a period of time t33 to time t34 and a period of time t35 to
time t36, the switch ST 154 used to shoot a still image is
operated. Therefore, during these periods, image data on the
"picture A" are also written onto the recording medium 193 after
being subjected to predetermined signal processing. The image data
on the "picture A" may also be written onto the recording medium
193 during the same period as that of the image data on the
"picture B" in addition to the period of time t33 to time t34 and
the period of time t35 to time t36.
In both of the "picture A" and the "picture B," it is assumed that
each piece of image data recorded on the recording medium 193 is a
moving image at the same frame rate, e.g., 60 fps, and the NTSC
time code is added. For example, the time code value added to each
frame of the moving image data is as illustrated in FIG. 17.
FIG. 18 is a diagram illustrating an example of the file structure
of image data on "picture A" and "picture B." Although an example
of MP4 file is illustrated as the format of image data here, the
format of image data is not limited to this. The MP4 file format is
standardized in ISO/IEC 14496-1/AMD6. All pieces of information are
stored in a structure called a Box, and composed of multiplexed
video and audio bit streams (media data) and management information
(meta data) on these pieces of media data. The box type of each Box
is represented by an identifier made up of four letters,
respectively. A file type Box 501 (ftyp) is located at the top of
the file as a Box to identify the file. In a media data Box 502
(mdat), the video and audio bit streams are multiplexed and stored.
In a movie Box 503 (moov), management information used to play back
a stored bit stream stored in the media data Box 502 is stored. A
skip Box 504 (skip) is a Box to skip data stored in the skip Box
504 during playback.
In the skip Box 504, a clip name 508 of a clip including this image
data file, and a clip UMID (Unique Material Identifier) 509
(CLIP-UMID) assigned to the material are stored. Also stored in the
skip Box 504 are a time code value (time code head value) 510 of a
clip head frame, and a serial number 511 of a recording medium on
which the material file is recorded. In FIG. 18, a free space 505,
user data 506, and meta data 507 are also contained in the skip Box
504. Since special data such as UMID of the material file and the
serial number of the recording medium are stored in the skip Box,
such data have no impact during playback on a general-purpose
viewer.
The same CLIP-UMID is set for respective MP4 files of the "picture
A" and "picture B." This enables a search for a file having the
same CLIP-UMID from one material file using the CLIP-UMID to
associate both files mechanically without any human confirmation
work.
FIG. 19 is a diagram for describing a shooting condition setting
screen for "picture A" and "picture B." It is assumed that the
shooting mode selecting lever 156 is rotated 90 degrees clockwise,
for example, from the position in FIG. 1B to enter a dual image
mode capable of shooting two images at the same time. A Bv value
521 corresponding to the brightness of an object at the time,
F-number 522, and respective ISO sensitivities 523, 524 and shutter
speeds 525, 526 of the "picture A" and the "picture B" are
displayed on the display unit 153. Further, picture modes 527, 528
currently set for the "picture A" and the "picture B" are
displayed, respectively. A picture mode to suit the purpose of
shooting can be selected from among plural options using the up and
down switches 158, 159, and the dial 160.
As mentioned above, the difference in light-receiving efficiency
between the photodiode 310A and the photodiode 310B is set as
three-step difference. Therefore, there is a three-step difference
in ISO sensitivity range between the "picture A" and the "picture
B." As illustrated in FIG. 20, the ISO sensitivity range of the
"picture A" is from ISO 100 to ISO 102400, and the ISO sensitivity
range of the "picture B" is from ISO 12 to ISO 12800.
FIG. 21 is a program AE (Automatic Exposure) chart in the dual
image mode. The abscissa indicates Tv value and corresponding
shutter speed, and the ordinate indicates Av value and
corresponding aperture value. Further, the diagonal direction is
equivalent Bv line. The relationship between the Bv value and the
ISO sensitivity of the "picture A" is represented in a gain
notation area 556, and the relationship between the Bv value and
the ISO sensitivity of the "picture B" is represented in a gain
notation area 557. In FIG. 21, each Bv value is represented as a
numeric value surrounded by a rectangle to distinguish from the
other parameters.
Referring to FIG. 21, it will be described how the shutter speed,
the aperture value, and the ISO sensitivity vary according to
variations from high brightness to low brightness.
First, when Bv value is 13, the ISO sensitivity of the "picture A"
is set to ISO 100. The equivalent Bv line of the "picture A"
intersects with a program chart 558 of the "picture A" at point
551, and it is determined from the point 551 that the shutter speed
is 1/4000 second and the aperture value is F11. On the other hand,
the ISO sensitivity of the "picture B" is set to ISO 12. The
equivalent Bv line of the "picture B" intersects with a program
chart 559 of the "picture B" at point 552, and it is determined
from the point 552 that the shutter speed is 1/500 second and the
aperture value is F11.
When Bv value is 10, the ISO sensitivity of the "picture A"
increases by one step and is set to ISO 200. The equivalent Bv line
of the "picture A" intersects with the program chart 558 of the
"picture A" at point 553, and it is determined from the point 553
that the shutter speed is 1/1000 second and the aperture value is
F11. On the other hand, the ISO sensitivity of the "picture B" is
set to ISO 12. The equivalent Bv line of the "picture B" intersects
with the program chart 559 of the "picture B" at point 560, and it
is determined from the point 560 that the shutter speed is 1/60
second and the aperture value is F11.
When Bv value is 6, the ISO sensitivity of the "picture A" is set
to ISO 200. The equivalent Bv line of the "picture A" intersects
with the program chart 558 of the "picture A" at point 554, and it
is determined from the point 554 that the shutter speed is 1/1000
second and the aperture value is F2.8. On the other hand, the ISO
sensitivity of the "picture B" is set to ISO 12. The equivalent Bv
line of the "picture B" intersects with the program chart 559 of
the "picture B" at point 555, and it is determined from the point
555 that the shutter speed is 1/60 second and the aperture value is
F2.8.
When Bv value is 5, the ISO sensitivity of the "picture A"
increases by one step and is set to ISO 400. The equivalent Bv line
of the "picture A" intersects with the program chart 558 of the
"picture A" at the point 554, and it is determined from the point
554 that the shutter speed is 1/1000 second and the aperture value
is F2.8. On the other hand, the ISO sensitivity of the "picture B"
is set to ISO 25. The equivalent Bv line of the "picture B"
intersects with the program chart 559 of the "picture B" at the
point 555, and it is determined from the point 555 that the shutter
speed is 1/60 second and the aperture value is F2.8.
After that, as the brightness is reduced, gain-up is performed to
increase the ISO sensitivity without changing the shutter speed and
the aperture value of both of the "picture A" and the "picture
B."
The exposure operation illustrated in this program AE chart is so
performed that the "picture A" will keep a shutter speed of 1/1000
second or faster over the entire brightness range written, and the
"picture B" will keep a shutter speed of 1/60 second over most of
the brightness range. Thus, a high-definition moving image with
less jerkiness can be obtained in the "picture B" while achieving
the stop motion effect in the "picture A."
FIG. 22 is a chart for describing a shutter speed difference
between the "picture A" and the "picture B" along an imaging
sequence. In FIG. 22, the abscissa is expressed in time to
illustrate a V synchronizing signal 481, accumulation periods 482,
483 of the "picture A," and accumulation periods 484, 485 of the
"picture B," where n denotes a frame number.
The accumulation period 482 is an accumulation period of a screen
upper edge line of the "picture A," and the accumulation period 483
is an accumulation period of a screen lower edge line of the
"picture A." Since the imaging element 184 performs exposure
operation with the function of a rolling electronic shutter, the
accumulation is started at predetermined time intervals
sequentially from the screen upper edge line toward the screen
lower edge line, and the accumulation is finished sequentially at
the time intervals. When the accumulation is completed, the signal
charge is read out sequentially from the imaging element 184, and
input to the analog front end 185. A period from time t53 to time
t54 is the accumulation period 482, and a period from time t55 to
time t56 is the accumulation period 483.
Further, the accumulation period 484 is an accumulation period of a
screen upper edge line of the "picture B," and the accumulation
period 485 is an accumulation period of a screen lower edge line of
the "picture B." Like in the "picture A," the accumulation in the
"picture B" is also started at predetermined time intervals from
the screen upper edge line toward the screen lower edge line, and
the accumulation is finished sequentially at the time intervals.
When the accumulation is completed, the signal charge is read out
sequentially from the imaging element 184, and input to the analog
front end 186. A period from time t51 to time t54 is the
accumulation period 484, and a period from time t52 to time t56 is
the accumulation period 485.
Although the two images of the "picture A" and the "picture B" are
shot in different accumulation time settings, similar levels of
signal charge are obtained in the imaging element 184, rather than
performing the gain-up on the "picture A." Therefore, both the
"picture A" and the "picture B" become noiseless images having
excellent S/N ratios.
FIG. 23 is a diagram illustrating a state of the display unit 153
during live view display after the imaging element 184 is powered
up. A sports scene of a person 163 captured through the
photographing optical system 152 is displayed on the display unit
153. Further, since the shooting mode selecting lever 156 is placed
in a position turned 90 degrees clockwise from the state in FIG.
1B, shutter speeds 491, 492 of the "picture A" and the "picture B,"
and an F-number 493 in the dual image mode are displayed.
FIG. 24A and FIG. 24B illustrate one frame among image frames
acquired by operating the switch ST 154 and the switch MV 155,
respectively. FIG. 24A is an image of the "picture A" shot with a
shutter speed of 1/1000 second and an aperture value of F4.0. FIG.
24B is an image of the "picture B" shot with a shutter speed of
1/60 second and an aperture value of F4.0. The image illustrated in
FIG. 24B is blurred due to such a slow shutter speed that the
motion of the object does not stop. However, if this image is
played back as a moving image at a frame rate of about 60 fps, this
blur will work rather well, leading to a smooth high-definition
image with less jerkiness. On the other hand, the stop motion
effect is supposed to be seen in the image illustrated in FIG. 24A
because the shutter speed is fast. However, as previously described
with reference to FIG. 15, signal charge generated inside the
silicon substrate leaks into adjacent pixel elements by diffusion
to result in a blurred image as if the image illustrated in FIG.
24B is added. This crosstalk phenomenon also occurs in the image
illustrated in FIG. 24B, but it is barely noticeable because the
image is originally blurred.
Therefore, in the imaging device according to the present
embodiment, a crosstalk correction to be described below is applied
to an image signal output from the imaging element 184 in order to
obtain an original stop motion effect by the fast shutter
speed.
FIG. 25 is a flowchart illustrating a series of processing
procedure steps including the crosstalk correction. Processing from
imaging to recording in the imaging device 100 according to the
present embodiment is performed, for example, in step S151 to step
S155 illustrated in FIG. 25.
In step S151, the accumulation of signal charge and readout of the
signal charge to the photodiodes 310A, 310B are performed according
to the sequence described with reference to FIG. 12 in response to
the operation of the switch MV 155 at time t32 as described with
reference to FIG. 16.
In step S152, signals read out from the imaging element 184 are
input to the analog front ends 185, 186, in which analog signals
are digitized.
In step S153, a correction (crosstalk correction) to reduce
crosstalk caused by the leakage of signal charge generated inside
the silicon substrate into adjacent pixel elements is performed.
The crosstalk correction is performed in the digital signal
processing units 187, 188. In other words, the digital signal
processing units 187, 188 function as crosstalk correction
units.
In step S154, development processing and compression processing as
needed are performed. In the development processing, a gamma
correction is performed as one of a series of processing steps. The
gamma correction is processing to apply a gamma function to an
input light amount distribution. As a result, the linearity of the
output with respect to the input light amount distribution is not
kept, and the crosstalk ratio also varies with the light amount at
the time. Therefore, as illustrated in FIG. 25, it is desired to
perform the crosstalk correction in a stage prior to step S154.
When the crosstalk correction is performed after the development,
the crosstalk processing may be changed depending on the magnitude
of the light amount, or the crosstalk correction may be performed
after the image signals are subjected to inverse gamma
correction.
In step S155, images are recorded on the recording medium 193.
Instead of or in addition to recording on the recording medium 193,
the images may also be stored in a storage device on a network 199
through the radio interface 198.
FIG. 26 is a diagram for describing the crosstalk correction
processing performed in step S153 by the digital signal processing
units 187, 188. Actual processing is performed as digital signal
processing.
In the digital signal processing unit 187, a signal 471A after
being subjected to A/D conversion processing is input to a
crosstalk amount correcting part 473A, and further input to a
crosstalk amount correcting part 473B via a crosstalk amount
calculating part 472A. Similarly, in the digital signal processing
unit 188, a signal 471B after being subjected to A/D conversion
processing is input to the crosstalk amount correcting part 473B,
and further input to the crosstalk amount correcting part 473A via
a crosstalk amount calculating part 472B.
In the crosstalk amount correcting part 473A, a crosstalk
correction is performed on the signal 471A based on the signal 471A
and the signal 471B after being subjected to a predetermined
calculation by a crosstalk correction function gij(n) in the
crosstalk amount calculating part 472B to obtain an output signal
474A. The output signal 474A is subjected to development and/or
compression processing as a subsequent processing step in the
digital signal processing unit 187.
In the crosstalk amount correcting part 473B, a crosstalk
correction is performed on the signal 471B based on the signal 471B
and the signal 471A after being subjected to a predetermined
calculation by a crosstalk correction function fij(n) in the
crosstalk amount calculating part 472A to obtain an output signal
474B. The output signal 474B is subjected to development and/or
compression processing as a subsequent processing step in the
digital signal processing unit 188.
Since the crosstalk depends on the amount of generated signal
charge, the crosstalk amount correcting parts 473A, 473B can
perform crosstalk corrections in a manner to correct an output
signal of one pixel element by a crosstalk amount corresponding to
the amount of signal charge generated in the other pixel element.
This can remove, from the output signal of the one pixel element, a
crosstalk component from the other pixel element, which is
superimposed on the output signal.
Here, data at a pixel address ij of the n-th frame of "picture A"
are denoted as DATA_Aij(n), data at a pixel address ij of the n-th
frame of "picture B" is denoted as DATA_Bij(n), and a correction
coefficient is denoted as .alpha.. Since the crosstalk depends on
the input light amount, corrected data C_DATA_Aij(n) at a pixel
address ij of the n-th frame of "picture A" can be expressed as
Equation (4). C_DATA_Aij(n)=DATA_Aij(n)-.alpha..times.DATA_Bij(n)
(4)
When a crosstalk correction function fij(n) is
fij(n)=-.alpha..times.DATA_Bij(n), Equation (4) can be expressed as
follows. C_DATA_Aij(n)=DATA_Aij(n)+fij(n).
Similarly, corrected data C_DATA_Bij(n) at a pixel address ij of
the n-th frame of "picture B" can be expressed as Equation (5) with
the correction coefficient denoted as .beta..
C_DATA_Bij(n)=DATA_Bij(n)-.beta..times.DATA_Aij(n) (5)
When a crosstalk correction function gij(n) is
gij(n)=-.beta..times.DATA_Aij(n), Equation (5) can be expressed as
follows. C_DATA_Bij(n)=DATA_Bij(n)+gij(n) (6).
As mentioned above, although crosstalk also occurs in the "picture
B," since it is barely noticeable because the image is originally
blurred, processing expressed in Equation (5) and Equation (6) may
be omitted. If the crosstalk correction is performed on an image
with a relatively short accumulation time without performing the
crosstalk correction on an image with a relatively long
accumulation time, the calculation load can be reduced.
FIG. 27 is a graph illustrating a specific example of the crosstalk
correction functions fij(n), gij(n). In FIG. 27, the abscissa
indicates the size of input data, and the ordinate indicates
crosstalk correction amount to be corrected. Both of the crosstalk
correction functions fij(n), gij (n) are functions to obtain
crosstalk correction amounts proportional to the input data,
respectively. Although both are different depending on the pixel
structure in a precise sense, the correction coefficient .alpha.
and the correction coefficient .beta. are nearly equal numeric
values. However, the degree of leakage of signal charge, generated
inside the silicon substrate depending on the incident angle of
light on each pixel element, into adjacent pixel elements by
diffusion is different. Therefore, the more the aperture 181 is
opened to increase the F-number, the larger the crosstalk and hence
the larger the absolute value of the crosstalk correction amount.
On the other hand, the more the aperture 181 is narrowed to
decrease the F-number, the smaller the crosstalk and hence the
smaller the absolute value of the crosstalk correction amount. In
FIG. 27, a characteristic 591 is a crosstalk correction function at
F2.8, a characteristic 592 is a crosstalk correction function at
F5.6, and a characteristic 593 is a crosstalk correction function
at F11. The gradients of the characteristic 591, the characteristic
592, and the characteristic 593 become smaller in this order. Note
that the F-number of the photographing optical system 152 can be
continuously changed. Therefore, if the correction coefficient
.alpha. and the correction coefficient .beta. are set as an
F-number function, more precise crosstalk corrections can be
achieved.
Further, as previously described with reference to FIG. 13, the
correction coefficient .alpha. and the correction coefficient
.beta. can be set as a function of the accumulation time of a
photodiode for "picture A" set to be relatively short.
The crosstalk correction amount can also be changed depending on
the image height to achieve further more accurate crosstalk
corrections. Since crosstalk increases when light enters the light
guide 255 obliquely, distance ZK from the optical axis 180 to each
pixel may be calculated based on the pixel address ij to apply a
crosstalk correction so as to increase the absolute value in
proportion to the distance ZK. Further, since the change in
incident angle of light on the light guide 255 depends also on
distance HK between an exit pupil of the photographing optical
system 152 and the imaging element 184, the crosstalk correction
function can be set as a function of the distance HK to perform
more precise corrections.
FIG. 28 is an image of "picture A" after the image of "picture A"
(FIG. 24A) shot with a shutter speed of 1/1000 second and an
aperture value of F4.0 is subjected to a crosstalk correction. In
the image of FIG. 24A, signal charge generated inside the silicon
substrate leaks into adjacent pixel elements by diffusion to result
in a blurred image as if the image illustrated in FIG. 24B were
added. On the other hand, in the image of FIG. 28, the original
stop motion effect by the fast shutter speed is achieved. On the
display unit 153 of a digital still motion camera, for example, it
is desired to be able to display both "picture A" 496 and "picture
B" 497 side by side or up and down as illustrated in FIG. 29 when
the playback button 161 is operated. Thus, the images can be
compared to check on the level of the stop motion effect. This
processing may also be performed in such a manner that image data
are supplied to a system or an apparatus through a network to cause
the system or a computer of the apparatus to read and execute a
program.
FIG. 30 is a diagram for describing a playback method in an image
playback device for data files including "picture A" and "picture
B" stored in a storage. As the image playback device, a tablet
terminal, a personal computer, a TV monitor, or the like can be
used in addition to the image playback device included in the
imaging device 100 described in the present embodiment. Components
(such as a CPU, a demodulation unit, and a display unit) are
provided in the device, such as the tablet terminal, the personal
computer, or the TV monitor, to play back a moving image file like
an MP4 file so as to serve as the image playback device. In the
imaging device 100 of the present embodiment, the function as the
image playback unit is implemented mainly by the system control CPU
178.
It is assumed here that data files of "picture A" and "picture B"
are stored in a storage on a network. In FIG. 30, a frame group 581
is a frame group of "picture A" stored in an MP4 file, and a frame
group 571 is a frame group of "picture B" stored in another MP4
file. The same CLIP-UMID is set for these MP4 files to associate
the MP4 files at the time of shooting.
When the playback of a moving image is started, frames are played
back sequentially from a head frame 572 of the frame group 571 of
"picture B" at a predetermined frame rate. Since the "picture B" is
shot in such a setting that the shutter speed is not excessively
fast ( 1/60 second in this example), the image playbacked is a
high-definition image with less jerkiness. In this specification, a
playback mode for a moving image file when the moving image is
playbacked at a frame rate higher than the frame rate at the time
of shooting may be represented as a presentation mode to change
presented images with time.
Suppose here that a user gives an instruction to change the
playback mode while a moving image of "picture B" is being
presented. For example, when the user pauses the playback at the
time where the playback progresses up to a frame 573, a frame 582
with the same time code is automatically retrieved from the data
file of the "picture A" associated with the "picture B," and the
frame 582 is displayed. The "picture A" is shot with a fast shutter
speed ( 1/1000 second in this example) at which the stop motion
effect can be easily obtained, i.e., the "picture A" is a powerful
image obtained by shooting a moment of the sports scene. Although
the two images of the "picture A" and the "picture B" are shot in
different accumulation time settings, similar levels of signal
charge are obtained in the imaging element 184, rather than
performing the gain-up on the "picture A." Therefore, both the
"picture A" and the "picture B" become noiseless images having
excellent S/N ratios.
Here, when printing is instructed, data on the frame 582 of the
"picture A" are output to the printer 195 through the print
interface 194. Thus, the print also become powerful one having the
stop motion effect that reflects the "picture A."
When the user releases the pause, the procedure automatically
returns to the frame group 571 of the "picture B" to resume
playback from a frame 574. At this time, the image to be played
back is a high-definition image with less jerkiness.
In the example of FIG. 30, although the frame presentation is
changed to the "picture A" when the playback of the "picture B" is
paused, the frame presentation may be changed to the "picture A"
when frame-by-frame playback of the "picture B" is performed. In
this specification, the playback mode for a moving image file when
playback is paused or frame-by-frame playback is performed may also
be referred to as the presentation mode without any change in
presented image with time. Further, the frame presentation may be
changed to the "picture A" when the playback is put in a mode to
reduce the frame rate to a certain rate or slower so as to perform
playback while checking the image continuously frame by frame. In
other words, it is convenient to present the "picture A" regardless
of the present or absence of an instruction to switch to the
presentation mode when the speed of frame-by-frame advance is
sufficiently slower than the normal playback frame rate (the frame
rate at the time of shooting).
The above difference in effect on the image played back is
considered to be caused by the difference in image presentation
method between the presentation to change the presented image with
time and the presentation (including the frame-by-frame playback)
without any change in presented image with time. In other words,
the presentation method varies according to a presentation
condition as to which of conflicting demands is important, a demand
for an image with less jerkiness or a demand for an image having a
high stop motion effect.
In the present embodiment, in view of the image acquisition feature
of the imaging device, an image based on signals from pixels whose
accumulation times are relatively long is presented in the
presentation (moving image presentation) to change the presented
image with time. On the other hand, an image based on signals from
pixels whose accumulation times are relatively short is presented
in the presentation (still image presentation) without any change
in presented image with time. Thus, images according to the
conflicting demands, i.e., the image with less jerkiness and the
image having a high stop motion effect, can be provided. This
effect is very beneficial.
The image presentation method illustrated in the present embodiment
can be used to provide images suitable for viewing of both of
moving image/still image when two or more images are shot at the
same time and viewed using a single imaging element.
Thus, according to the present embodiment, images suitable for
viewing of both of a moving image and a still image can be acquired
and played back.
Second Embodiment
An imaging device according to a second embodiment of the present
invention will be described with reference to FIG. 31A to FIG. 31E.
The same constituent elements as those of the imaging device
according to the first embodiment illustrated in FIG. 1A to FIG. 30
are given the same reference numerals to omit or simplify the
description.
In the first embodiment, the method of generating two or more
moving image files in consideration of compatibility with
conventional file formats and automatically associating these
moving image files is illustrated.
In the present embodiment, an example of another preferred file
format, and association between "picture A" and "picture B" in this
example will be described. Note that the configuration of the
imaging device used to obtain "picture A" and "picture B" is the
same as that of the first embodiment.
FIG. 31A is a schematic view illustrating the method described in
the first embodiment. FIG. 31B is a schematic view illustrating a
method to be described in the present embodiment. FIG. 31C, FIG.
31D, and FIG. 31E are diagrams for specifically describing image
storing methods in the present embodiment.
In the method of the first embodiment, as illustrated in FIG. 31A,
the system control CPU 178 separately generates a file 6001 as a
moving image file of "picture A" and a file 6002 as a moving image
file of "picture B." The system control CPU 178 has the function as
a moving image file generating unit. The file 6001 and the file
6002 are associated using CLIP-UMID as described in the first
embodiment. In other words, the file 6001 contains a moving image
of "picture A," and synchronization information for synchronizing
the moving image of "picture A" and a moving image of "picture B"
frame by frame. The file 6002 contains the moving image of "picture
B," and synchronization information for synchronizing the moving
image of "picture A" and the moving image of "picture B" frame by
frame.
In contrast, in the method of the present embodiment, the system
control CPU 178 generates one file 6003 from moving image data on
"picture A" and moving image data on "picture B" as illustrated in
FIG. 31B. Specific examples of storage methods into the file 6003
are illustrated in FIG. 31C to FIG. 31E.
The method illustrated in FIG. 31C is an example of using a stereo
image format, so-called side-by-side. Since no parallax between
"picture A" and "picture B" obtained by the imaging device of the
first embodiment as illustrated in FIG. 5, a three-dimensional
image is not obtained even using the stereo image format.
Information is just stored using the stereo image format.
In the case of a stereo image, there is proposed a method
(side-by-side) as one of methods for recoding an image presented to
the right eye and an image presented to the left eye to store these
images as one image with the images set laterally side-by-side. In
the example of FIG. 31C, this method is used to store an image of
"picture A" and an image of "picture B" as one image data with the
images arranged as illustrated. The image of "picture A" and the
image of "picture B" stored as one image are acquired in sync with
a synchronization period. When focusing on a specific frame 6004 at
this time, data on the frame 6004 is an image double in size in the
lateral direction and composed of an image 6005 of "picture A" and
an image 6006 of "picture B" that lie next to each other. In other
words, the file 6003 is a moving image file in which each frame
contains a frame image of a moving image of "picture A," and a
frame image of a moving image of "picture B" acquired in sync with
that of "picture A."
When the playback of the moving image is started, frame images are
played back sequentially at a set frame rate from the head frame of
a frame group of "picture B." In other words, in a playback device,
only an image to be present to one eye in the stereo image format
is continuously presented. In the side-by-side method, an area
corresponding to the "picture B" can be clipped and presented.
Since the "picture B" is shot in such a setting that the shutter
speed will not be excessively fast ( 1/60 second in this example),
the image played back is a high-definition image with less
jerkiness.
For example, when the user pauses the playback at the time where
the playback progresses up to the frame 6004, the image 6005 of
"picture A" corresponding to the image 6006 of "picture B" is
automatically displayed. In other words, the image is switched to
an image to be presented to the other eye in the stereo image
format. The "picture A" is shot with a fast shutter speed ( 1/1000
second in this example) at which the stop motion effect can be
easily obtained, i.e., the "picture A" is a powerful image obtained
by shooting a moment of the sports scene. Although the two images
of the "picture A" and the "picture B" are shot in different
accumulation time settings, similar levels of signal charge are
obtained in the imaging element 184, rather than performing the
gain-up on the "picture A." Therefore, both the "picture A" and the
"picture B" become noiseless images having excellent S/N
ratios.
The method illustrated in FIG. 31D is an example of using another
stereo image format suitable for a so-called liquid-crystal shutter
type playback device. In the playback device using a liquid-crystal
shutter, images are presented by switching an image presented to
the right eye and an image presented to the left eye in a
time-division manner. Using this format, the "picture A" and the
"picture B" can be stored in one file. For example, when the frame
rate of an image at the time of shooting is designated as 60 fps,
the "picture A" and the "picture B" are alternately stored as
frames of a moving image at 120 fps, which is twice the frame rate.
For example, a pair of an image of "picture A" and an image of
"picture B" acquired in sync with each other are stored as data on
frames 6007 and 6008. Then, a pair of an image of "picture A" and
an image of "picture B" acquired in sync with each other at the
next timing are stored as data on frames 6009 and 6010. When
focusing only on data of either the "picture A" or the "picture B,"
the data thus stored are data on a moving image at the same frame
rate of 60 fps as that of the shooting time. In other words, the
file 6003 is a moving image file recorded to present frames of a
moving image of "picture A" and frames of a moving image of
"picture B" alternately. Then, the frames of the moving image of
"picture A" and the frames of the moving image of "picture B"
synchronized with each other are continuously recorded in this
moving image file.
When the playback of the moving image is started, frame images are
played back sequentially at a set frame rate from the head frame of
a frame group of "picture B." In other words, in the playback
device, only an image to be present to one eye in the stereo image
format is continuously presented. In the example of FIG. 31D, every
other frame can be played back to present only the "picture B."
For example, when the user pauses the playback at the time where
the playback progresses up to the frame 6008, an image of the frame
6007 of "picture A" corresponding to the image of the frame 6008 of
"picture B" is displayed. Thus, images suitable for viewing of both
of moving image/still image can be provided.
The method illustrated in FIG. 31E is an example of using a format
to store, in one file, two or more moving images as a multitrack
moving image. The format of FIG. 31E is a format capable of storing
an auxiliary image, a parallax image, and the like as two or more
tracks. Here, "picture B" is recorded as a main image 6012 of track
1, "picture A" is recorded as an auxiliary image 6011 of track 2,
and information on the imaging device and the like is stored in a
meta data recording part. Moving images on the two or more tracks
correspond to one time code. In other words, a file 6003 is a
moving image file including a first moving image track containing a
moving image of "picture A" and synchronization information, and a
second moving image track containing a moving image of "picture B"
and synchronization information.
When the playback of the moving image is started, frame images are
played back sequentially at a set frame rate from the head frame of
a frame group of "picture B." In other words, in the playback
device, the image of track is presented. When the user pauses the
playback, an image of track 2 corresponding to the same time code
can be presented. Thus, images suitable for viewing of both of
moving image/still image can be provided.
Third Embodiment
An imaging device according to a third embodiment of the present
invention will be described with reference to FIG. 32 to FIG. 38.
The same constituent elements as those of the imaging devices
according to the first and second embodiments illustrated in FIG.
1A to FIG. 31E are given the same reference numerals to omit or
simplify the description.
In the first and second embodiments, the two photodiodes 310A, 310B
different in light-receiving efficiency (sensitivity) are used
depending on the accumulation time to enable moving image shooting
suitable for various shooting scenes. In the present embodiment, an
example of controlling the accumulation time of one photodiode to
achieve the same effect as that of the first and second embodiments
will be described.
The imaging device according to the present embodiment is the same
as the imaging device according to the first embodiment except that
the circuit configuration of the pixels 303 of the imaging element
184 is different.
FIG. 32 is a circuit diagram illustrating a circuit configuration
of the pixels 303 of the imaging element 184 of the imaging device
according to the present embodiment. FIG. 32 illustrates a pixel
303 in the first column and the first row and a pixel 303 in the
first column and the m-th row among the plurality of pixels 303
that constitute the pixel array 302. As illustrated in FIG. 32,
each pixel 303 includes a photodiode 600, transfer transistors
601A, 601B, 602A, 602B, and 603, a reset transistor 604, an
amplifier transistor 605, and a select transistor 606.
The anode of the photodiode 600 is connected to the ground line.
The cathode of the photodiode 600 is connected to the source of the
transfer transistor 601A, the source of the transfer transistor
601B, and the source of the transfer transistor 603, respectively.
The drain of the transfer transistor 601A is connected to the
source of the transfer transistor 602A. A connection node between
the drain of the transfer transistor 601A and the source of the
transfer transistor 602A forms a signal holding unit 607A. The
drain of the transfer transistor 601B is connected to the source of
the transfer transistor 602B. A connection node between the drain
of the transfer transistor 601B and the source of the transfer
transistor 602B forms a signal holding unit 607B.
The drain of the transfer transistor 602A and the drain of the
transfer transistor 602B are connected to the source of the reset
transistor 604 and the gate of the amplifier transistor 605. A
connection node of the drain of the transfer transistor 602A, the
drain of the transfer transistor 602B, the source of the reset
transistor 604, and the gate of the amplifier transistor 605 forms
a floating diffusion region 608. The source of the amplifier
transistor 605 is connected to the drain of the select transistor
606. The drain of the reset transistor 604 and the drain of the
amplifier transistor 605 are connected to a power source line 620.
The drain of the transfer transistor 603 is connected to a power
source line 621. The source of the select transistor 606 is
connected to a signal output line 623.
Thus, each pixel 303 of the imaging element 184 of the imaging
device according to the present embodiment includes two signal
holding units 607A, 607B for one photodiode 600. Since the basic
structure of a CMOS type imaging element 184 having signal holding
units is disclosed, for example, in Japanese Patent Application
Laid-Open No. 2013-172210 by the applicant of the present
application, detailed description thereof will be omitted here.
The plurality of pixels 303 of the pixel array 302 are connected in
units of rows to control lines arranged in the row direction from
the vertical scanning circuit 307. The control lines in each row
include a plurality of control lines connected to the gates of the
transfer transistors 601A, 602A, 601B, 602B, and 603, the reset
transistor 604, and the select transistor 606, respectively. The
transfer transistor 601A is controlled by a transfer pulse
.phi.TX1A, and the transfer transistor 602A is controlled by a
transfer pulse .phi.TX2A. The transfer transistor 601B is
controlled by a transfer pulse .phi.TX1B, and the transfer
transistor 602B is controlled by a transfer pulse .phi.TX2B. The
reset transistor 604 is controlled by a reset pulse .phi.RES, and
the select transistor 606 is controlled by a select pulse .phi.SEL.
The transfer transistor 603 is controlled by a transfer pulse
.phi.TX3. Each control pulse is sent out from the vertical scanning
circuit 307. Each transistor is on-state when the control pulse is
at the high level, and off-state when the control pulse is at the
low level.
The imaging element 184 that forms part of the imaging device of
the present embodiment includes the two signal holding units 607A,
607B for one photodiode 600. This enables a first moving image
having a stop motion effect and a second moving image with less
jerkiness to be shot at the same time. Therefore, two images
different in accumulation period can be read out without reducing
the S/N ratios.
The shooting conditions for the first moving image (corresponding
to "picture A") and the second moving image (corresponding to
"picture B") in the imaging device may be set in the same way as
those in the first and second embodiments.
FIG. 33 is a program AE chart in the dual image mode. The abscissa
indicates Tv value and corresponding shutter speed, and the
ordinate indicates Av value and corresponding aperture value.
Further, the diagonal direction is equivalent Bv line. The
relationship between the Bv value and the ISO sensitivity of the
first moving image ("picture A") is represented in a gain notation
area 556, and the relationship between the Bv value and the ISO
sensitivity of the second moving image ("picture B") is represented
in a gain notation area 557. In FIG. 33, each Bv value is
represented as a numeric value surrounded by a rectangle to
distinguish from the other parameters.
Referring to FIG. 33, it will be described how the shutter speed,
the aperture value, and the ISO sensitivity vary according to
variations from high brightness to low brightness. Since the
imaging device of the present embodiment is used to shoot the first
moving image and the second moving image at the same time, the same
aperture value is set for the same object brightness in the program
AE chart.
First, when Bv value is 14, the ISO sensitivity of the first moving
image is set to ISO 100. The equivalent Bv line of the first moving
image intersects with a program chart 558 of the first moving image
at point 551, and it is determined from the point 551 that the
shutter speed is 1/4000 second and the aperture value is F11. On
the other hand, the ISO sensitivity of the second moving image is
set to ISO 1. The equivalent Bv line of the second moving image
intersects with a program chart 559 of the second moving image at
point 552, and it is determined from the point 552 that the shutter
speed is 1/60 second and the aperture value is F11.
When Bv value is 11, the ISO sensitivity of the first moving image
increases by one step and is set to ISO 200. The equivalent Bv line
of the first moving image intersects with the program chart 558 of
the first moving image at point 553, and it is determined from the
point 553 that the shutter speed is 1/1000 second and the aperture
value is F11. On the other hand, the ISO sensitivity of the second
moving image is set to ISO 12. The equivalent Bv line of the second
moving image intersects with the program chart 559 of the second
moving image at the point 552, and it is determined from the point
552 that the shutter speed is 1/60 second and the aperture value is
F11.
When Bv value is 7, the ISO sensitivity of the first moving image
is set to ISO 200. The equivalent Bv line of the first moving image
intersects with the program chart 558 of the first moving image at
point 554, and it is determined from the point 554 that the shutter
speed is 1/1000 second and the aperture value is F2.8. On the other
hand, the ISO sensitivity of the second moving image is set to ISO
12. The equivalent Bv line of the second moving image intersects
with the program chart 559 of the second moving image at point 555,
and it is determined from the point 555 that the shutter speed is
1/60 second and the aperture value is F2.8.
When Bv value is 6, the ISO sensitivity of the first moving image
increases by one step and is set to ISO 400. The equivalent Bv line
of the first moving image intersects with the program chart 558 of
the first moving image at the point 554, and it is determined from
the point 554 that the shutter speed is 1/1000 second and the
aperture value is F2.8. On the other hand, the ISO sensitivity of
the second moving image is set to ISO 25. The equivalent Bv line of
the second moving image intersects with the program chart 559 of
the second moving image at the point 555, and it is determined from
the point 555 that the shutter speed is 1/60 second and the
aperture value is F2.8.
After that, as the brightness is reduced, gain-up is performed to
increase the ISO sensitivity without changing the shutter speed and
the aperture value of both of the first moving image and the second
moving image.
The exposure operation illustrated in this program AE chart is so
performed that the first moving image will keep a shutter speed of
1/1000 second or faster over the entire brightness range written,
and the second moving image will keep a shutter speed of 1/60
second over the entire brightness range. Thus, a high-definition
moving image with less jerkiness can be obtained in the second
moving image while achieving the stop motion effect in the first
moving image.
In the meantime, the first moving image and the second moving image
shot with the same aperture value at the same time are controlled
to be different in ISO sensitivity from each other. However, when
exposure control is performed to make the exposure of the first
moving image proper, the signal of the second moving image is so
saturated that the ISO sensitivity cannot be controlled. Therefore,
in the imaging device according to the present embodiment, a short
accumulation period is performed Np times (where Np is an integer
of 2 or more (Np>1)) at equal intervals while the shutter speed
is 1/60 second corresponding to the frame rate of the second moving
image. Then, the charge accumulated between respective accumulation
periods performed Np times is added up to generate an image to make
the ISO sensitivity virtually low.
In the present embodiment, a period corresponding to the shutter
speed of 1/60 second of the second moving image is set as a period
during which accumulation in the short accumulation period
performed Np times for the second moving image is performed.
Further, a period corresponding to the shutter speed of 1/1000
second of the first moving image is set as an accumulation period
for the first moving image (i.e., the accumulation time for the
first moving image is 1/1000 second). Then, the short accumulation
period for the second moving image is so controlled that the total
accumulation time for the second moving image will become equal to
the accumulation time for the first moving image.
In other words, the total accumulation time for the second moving
image generated by adding up charge accumulated during the short
accumulation period performed Np times during the period
corresponding to the shutter speed of the second moving image is
controlled to become equal to the accumulation time for the first
moving image. Further, each of the accumulation times of Np times
of accumulation periods for one second moving image is so
controlled that the ISO sensitivity of the second moving image will
become equal to the ISO sensitivity of a first moving image shot
during the shooting period of the second moving image.
As an example, suppose that when the brightness is Bv7, charge is
accumulated and added up 16 times during the period corresponding
to the shutter speed of 1/60 second to generate the second moving
image. In this case, each of the accumulation times of Np times of
accumulation periods for generation of the second moving image is
set to 1/16000 second to make the ISO sensitivity of the second
moving image equivalent to the ISO sensitivity (ISO 200) of the
first moving image.
FIG. 34 is a flowchart of shooting operation in the dual image mode
to shoot the first moving image and the second moving image at the
same time. Since the first moving image is suitable for viewing of
a still image having the stop motion effect, the first moving image
may be referred to as "still image" and the second moving image may
be referred to as "moving image" in the following description to
distinguish between the first moving image and the second moving
image. Further, the shooting mode in the present embodiment may be
called a "moving image/still image shooting mode" for descriptive
purposes.
When the first moving image and the second moving image are shot at
the same time, the imaging device of the present embodiment can
perform shooting in either of a moving image shooting mode capable
of shooting a smooth moving image and a moving image shooting mode
in which rolling distortion generally produced in a CMOS-type
imaging element is not generated. Therefore, in the present
embodiment, either a first moving image/still image shooting mode
capable of shooting a smooth moving image or a second moving
image/still image shooting mode capable of shooting a moving image
without rolling distortion is selected depending on the shutter
speed of the first moving image. Referring to the flowchart of FIG.
34, shooting operation in the dual image mode will be described
below.
First, in step S501, the system control CPU 178 as a control unit
of the imaging device checks on a moving image/still image shooting
mode set by a person who performs shooting. When checking that the
shooting mode is the dual image mode to shoot the first moving
image and the second moving image at the same time, the system
control CPU 178 proceeds to step S502.
Then, in step S502, the system control CPU 178 checks on a set
shooting period of the second moving image.
Then, in step S503, the system control CPU 178 checks on a shutter
speed (still image shutter speed) of the first moving image set by
the person who performs shooting.
Then, in step S504, the system control CPU 178 determines whether
the set shutter speed of the first moving image is faster than a
predetermined value. When determining that the shutter speed of the
first moving image is set to a shutter speed faster than a
predetermined shutter speed Tth to obtain an image having the stop
motion effect on an object moving fast (yes), the system control
CPU 178 proceeds to step S505. In step S505, the system control CPU
178 sets the moving image/still image shooting mode to the second
moving image/still image shooting mode (undistorted moving image
shooting mode) in which rolling distortion is not generated, and
proceeds to step S507.
On the other hand, when determining that the shutter speed of the
first moving image is set to a shutter speed slower than the
predetermined shutter speed Tth (no), the system control CPU 178
proceeds to step S506. In step S506, the system control CPU 178
sets the moving image/still image shooting mode to the first moving
image/still image shooting mode (smooth moving image shooting mode)
capable of shooting a smooth moving image, and proceeds to step
S507.
When the moving image/still image shooting mode is set in step S505
or step S506, the system control CPU 178 sets, in step S507, a
control method for the imaging element 184 according to the set
moving image/still image shooting mode. The control methods for the
imaging element 184 in the first moving image/still image shooting
mode and the second moving image/still image shooting mode will be
described later.
Then, in step S508, the system control CPU 178 checks on the state
of the switch MV 155 as a button used to start and stop moving
image shooting through the switch input unit 179 to determine
whether to start shooting. When the start of moving image shooting
is not instructed at the switch MV 155 (no), the system control CPU
178 returns to step S501 to repeat the procedure from checking on
the moving image/still image shooting mode. On the other hand, when
the start of moving image shooting is instructed at the switch MV
155 (yes), the system control CPU 178 proceeds to step S509.
In step S509, the system control CPU 178 controls the aperture 181
of the photographing optical system 152 through the aperture
control unit 182 based on AE information on images captured before
then and the set shutter speed of the first moving image.
Then, in step S510, the system control CPU 178 drives the imaging
element 184 through the timing generation unit 189 to perform
shooting. In the present embodiment, since the shooting mode is the
dual image mode to shoot the first moving image and the second
moving image at the same time, the shooting operation is performed
by the switch MV 155 as the button to start and stop moving image
shooting. The shooting operation is performed according to the
control method for the imaging element 184 set in step S507. The
control method for the imaging element 184 will be described
later.
Then, in step S511, the system control CPU 178 checks on the state
of the switch MV 155 as the button to start and stop moving image
shooting through the switch input unit 179 to determine whether the
shooting is completed. When the switch MV 155 is set in a shooting
state (no), the system control CPU 178 returns to step S509 to
continue shooting. On the other hand, when the switch MV 155 is set
in a shooting stopped state (yes), the system control CPU 178
proceeds to step S512 to stop shooting.
FIG. 35 is a chart for describing the accumulation and readout
timings of the imaging element 184 in the imaging device of the
present embodiment when the first moving image and the second
moving image are shot at the same time in the first moving
image/still image shooting mode capable of shooting a smooth moving
image. The term "accumulation" here means operation for
transferring and accumulating charge generated in the photodiode
600 to and in the signal holding units 607A, 607B. The term
"readout" means operation for outputting signals based on the
charges, held in the signal holding units 607A, 607B, to the
outside of the imaging element 184 via the floating diffusion
region 608.
In FIG. 35, the abscissa is expressed in time to illustrate a
vertical synchronization signal 650, a horizontal synchronization
signal 651, a still image accumulation period 661, a still image
transfer period 662, a still image readout period 665, a moving
image accumulation period 663, a moving image transfer period 664,
and a moving image readout period 666. Here, the still image
accumulation period 661 indicates an accumulation period of signal
charge for the first moving image into the photodiode 600. The
still image transfer period 662 indicates a period of transferring
the signal charge for the first moving image from the photodiode
600 to the signal holding unit 607A. The still image readout period
665 indicates a readout period of the first moving image. The
moving image accumulation period 663 indicates an accumulation
period of signal charge for the second moving image into the
photodiode 600. The moving image transfer period 664 indicates a
period of transferring the signal charge for the second moving
image from the photodiode 600 to the signal holding unit 607B. The
moving image readout period 666 indicates a readout period of the
second moving image.
In this driving example, the first moving image and the second
moving image are read out during each cycle of the vertical
synchronization signal 650. Further, timings of 16 rows are
illustrated in FIG. 35 for descriptive purposes, but the actual
imaging element 184 has thousands of rows. In FIG. 35, the final
row is the m-th row.
The first moving image is generated based on signal charge
generated during one accumulation period (still image accumulation
period 661) performed simultaneously in all rows during each cycle
(time Tf) of the vertical synchronization signal 650. The second
moving image is generated based on signal charge obtained by adding
up signal charges respectively generated during accumulation
periods (moving image accumulation periods 663) divided by the
number of Np times (where Np is an integer of 2 or more (Np>1)).
Np as the number of accumulation periods of the second moving image
performed during one shooting period is, for example, 16 times, and
these accumulation periods are performed at equal time intervals.
The interval (time Tf) of the vertical synchronization signal 650
is 1/60 second, which approximately corresponds to a period during
which Np times of accumulation periods of the second moving image
are performed in the first moving image/still image shooting mode.
The accumulation of the first moving image is performed during the
readout of the second moving image (moving image readout period
666) in one shooting period.
This enables shooting of the first moving image and the second
moving image at the same time. An image having no blur can also be
acquired as the first moving image at a short accumulation time
intended by the person who performs shooting. Further, Np times of
accumulation periods performed at equal time intervals virtually
mean one long accumulation period from the start time of the first
accumulation period to the end time of the Np-th accumulation
period. Therefore, a smooth image with less jerkiness can be
acquired as the second moving image.
In FIG. 35, the accumulation period of the first moving image
(still image accumulation period 661) is set to a time
corresponding to a shutter speed T1 set by the person who performs
shooting. In this driving example, the shutter speed T1 is set to
1/500 second. The accumulation period of the first moving image is
set to be performed simultaneously in all rows and be completed
immediately before the start of readout of the first moving image
in the first row (still image readout period 665). The end time of
the accumulation period of the first moving image is a time after a
lapse of time Ta from the vertical synchronization signal 650. The
time Ta is set to be half or less of the interval Tf of the
vertical synchronization signal 650. Since the end time of the
accumulation period of the first moving image (still image
accumulation period 661) is the same in all rows, the start time of
the accumulation period of the first moving image with respect to
the vertical synchronization signal 650 is set according to the
shutter speed T1 of the first moving image.
On the other hand, the accumulation period of the second moving
image (moving image accumulation period 663) is performed plural
times at equal time intervals during each cycle. In this driving
example, the time interval is set to complete the accumulation
period divided into 16 times immediately before the start of the
readout of each row (moving image readout period 666). The time
interval of the accumulation period of the second moving image may
be set to be a multiple of an integer for the interval Th of the
horizontal synchronizing signal 651. Thus, the accumulation timing
of the second moving image in each row is the same as that in the
other rows. In FIG. 35, the time interval of the accumulation
period of the second moving image is illustrated to be twice the
interval Th of the horizontal synchronization signal 651 for
descriptive purposes. When the number of rows of the imaging
element 184 is denoted by m, and the number of accumulations of the
second moving image during each cycle is denoted by Np, the time
interval of the accumulation period of the second moving image is
generally set to a value obtained by multiplying an integer not
exceeding m/Np by the interval Th of the horizontal synchronization
signal 651.
Further, one accumulation time of the second moving image is set to
T1/Np (= 1/8000 second). The start time of the accumulation period
of the second moving image in each row is fixed with respect to the
vertical synchronization signal 650. The end time of one
accumulation period of the second moving image is set with respect
to the vertical synchronization signal 650 depending on the still
image shutter speed T1 set by the person who performs shooting.
In FIG. 35, since the accumulation time (T1) of the first moving
image is long, the number of accumulations Np of the second moving
image during each cycle is 14 times. Therefore, the second moving
image generated during one shooting period is corrected using the
first moving image generated during the same shooting period.
Referring next to a timing chart of FIG. 36, an example of the
control method for the imaging element 184 during the shooting
period starting at time t1 in FIG. 35 will be described. Time t1 at
which a vertical synchronization signal .PHI.V rises in FIG. 36 is
the same as time t1 at which the vertical synchronization signal
650 rises in FIG. 35.
It is assumed here that the imaging element 184 has m rows of
pixels in the vertical direction. In FIG. 36, the timings of the
first row and the m-th row as the final row are illustrated among
the m rows. In FIG. 36, a signal .PHI.V is the vertical
synchronization signal, and a signal .PHI.H is the horizontal
synchronization signal.
First, at time t1, the vertical synchronization signal .PHI.V and
the horizontal synchronization signal .PHI.H supplied from the
timing generation unit 189 are changed from the low level to the
high level.
Then, at time t2 synchronized with the change of the vertical
synchronization signal .PHI.V to the high level, a reset pulse
.PHI.RES(1) for the first row supplied from the vertical scanning
circuit 307 is changed from the high level to the low level. This
causes the reset transistor 604 of each pixel 303 in the first row
to be turned off to release the reset state of the floating
diffusion region 608. Simultaneously, a select pulse .PHI.SEL(1)
for the first row supplied from the vertical scanning circuit 307
is changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the first row to be
turned on to enable the readout of an image signal from each pixel
303 in the first row.
Then, at time t3, a transfer pulse .PHI.TX2B(1) for the first row
supplied from the vertical scanning circuit 307 is changed from the
low level to the high level. This causes the transfer transistor
602B of each pixel 303 in the first row to be turned on to
transfer, to the floating diffusion region 608, signal charge of
the second moving image accumulated in the signal holding unit 607B
during the previous shooting period (a shooting period completed at
time t1). As a result, a signal corresponding to a change in the
potential of the floating diffusion region 608 is read out into the
signal output line 623 via the amplifier transistor 605 and the
select transistor 606. The signal read out into the signal output
line 623 is supplied to an unillustrated readout circuit, and
output to the outside as an image signal of the second moving image
of each pixel in the first row (corresponding to the moving image
readout period 666 in FIG. 35).
Then, at time t4, a transfer pulse .PHI.TX2B(1) for the first row
and transfer pulses .PHI.TX2A (.PHI.TX2A(1), .PHI.TX2A(m)) for all
rows supplied from the vertical scanning circuit 307 are changed
from the low level to the high level. This causes the transfer
transistor 602B of each pixel 303 in the first row and the transfer
transistors 602A of the pixels 303 in all rows to be turned on. At
this time, the reset pulses .PHI.RES (.PHI.RES(1), .PHI.RES(m)) in
all rows are already changed to the high level, and hence the reset
transistors 604 are in the on-state. Thus, the floating diffusion
regions 608 of the pixels 303 in all rows, the signal holding units
607A of the pixels 303 in all rows, and the signal holding unit
607B of each pixel 303 in the first row are reset. At this time,
the select pulse .PHI.SEL(1) in the first row is also changed to
the low level, and each pixel 303 in the first row is returned to
an unselected state.
Then, at time t5, transfer pulses .PHI.TX3 (.PHI.TX3(1),
.PHI.TX3(m)) for all rows supplied from the vertical scanning
circuit 307 are changed from the high level to the low level. This
causes the transfer transistors 603 in all rows to be turned off to
release the reset of the photodiodes 600 of the pixels 303 in all
rows so as to start the accumulation of signal charge of the second
moving image in the photodiodes 600 of the pixels 303 in all rows
(corresponding to the moving image accumulation period 663 in FIG.
35).
Here, a time interval Tb between time t1, at which the vertical
synchronization signal .PHI.V becomes the high level, and time t5,
at which the accumulation of signal charge of the second moving
image in the photodiodes 600 of the pixels 303 in all rows is
started, is fixed.
Note that the start of the accumulation period of the first row of
the second moving image at time t5 in FIG. 36 represents the start
of the accumulation period of the second moving image in the
shooting period from time t1 in FIG. 35. Further, the start of the
accumulation period of the m-th row of the second moving image at
time t5 represents the start of the accumulation period of the
second moving image in the shooting period before time t1 in FIG.
35.
Then, immediately before time t7, transfer pulses .PHI.TX1B
(.PHI.TX1B(1), .PHI.TX1B(m)) for all rows supplied from the
vertical scanning circuit 307 are changed from the low level to the
high level. This causes the transfer transistors 601B of the pixels
303 in all rows to be turned on to transfer, to the signal holding
units 607B, the signal charges accumulated in the photodiodes 600
of the pixels 303 in all rows (corresponding to the moving image
transfer period 664 in FIG. 35).
Then, at time t7, the transfer pulses .PHI.TX1B (.PHI.TX1B(1),
.PHI.TX1B(m)) for all rows are changed from the high level to the
low level. This causes the transfer transistors 601B of the pixels
303 in all rows to be turned off to complete the transfer of the
signal charges accumulated in the photodiodes 600 to the signal
holding units 607B.
A period from time t5 to time t7 corresponds to the accumulation
time (=T1/16) in each of the Np accumulation periods of the second
moving image.
Similarly, at time t7, the transfer pulses .PHI.TX3 (.PHI.TX3(1),
.PHI.TX3(m)) for all rows are changed from the low level to the
high level. This causes the transfer transistors 603 of the pixels
303 in all rows to be turned on to put the photodiodes 600 of the
pixels 303 in all rows into the reset state.
The second accumulation period of the second moving image is
started at time t8 after a lapse of the time twice the interval Th
of the horizontal synchronization signal .phi.H from time t5 at
which the first accumulation period of the second moving image in
the shooting period starting at time t1 is started.
Since the operation of the second accumulation period of the second
moving image starting at time t8 and ending at time t10 is the same
as the operation of the first accumulation period of the second
moving image starting at time t5 and ending at time t7 as mentioned
above, the description thereof will be omitted.
Here, in the operation of the first and the second accumulation
periods of the second moving image, signal charges of the second
moving image generated during these two accumulation periods are
added up and held in the signal holding unit 607B.
Then, during a period from time t10 to time t11, the third to fifth
accumulation periods of the second moving image are performed in
the same manner as the period from time t5 to time t7 as mentioned
above.
Then, the sixth accumulation period of the second moving image is
started at time t11. Here, the start time t11 of the sixth
accumulation period of the second moving image is set to the time
after a lapse of the time T (=6.times.2.times.Th+Tb) from time t1
at which the vertical synchronization signal .PHI.V becomes the
high level. Here, Th denotes the time interval of the horizontal
synchronization signal .PHI.H, and Tb denotes a time interval
between time t1 at which the vertical synchronization signal .PHI.V
becomes the high level and time t5 at which the first accumulation
period of the second moving image is started in the photodiode
600.
Since the operation of the sixth accumulation period of the second
moving image starting at time t11 and ending at time t13 is the
same as the operation of the first accumulation period of the
second moving image starting at time t5 and ending at time t7 as
mentioned above, the description thereof will be omitted.
Then, the accumulation period of the first moving image as the
first image is started at time t14. In this driving example, the
number of accumulation periods of the first moving image in one
shooting period is once. The start time of the readout period of
the first moving image (corresponding to the still image readout
period 665 in FIG. 35) with respect to the vertical synchronization
signal .PHI.V is fixed. Therefore, the end time of the accumulation
period of the first moving image with respect to the vertical
synchronization signal .PHI.V is fixed to a time after a lapse of
time Ta from the start time, and the accumulation period of the
first moving image is set to be completed at time t19. Here, a time
interval from time t1 to time t19 corresponds to time Ta in FIG.
35. The start time of the accumulation period of the first moving
image is controlled based on the shutter speed T1 of the first
moving image set by the person who performs shooting.
At time t14 back by time T1 from time t19 as the end time of the
accumulation period of the first moving image, the transfer pulses
.PHI.TX3 (.PHI.TX3(1), .PHI.TX3(m)) for all rows are changed from
the high level to the low level. This causes the transfer
transistors 603 of the pixels 303 in all rows to be turned off to
release the reset of the photodiodes 600 of the pixels 303 in all
rows. Then, the accumulation period of signal charge of the first
moving image in the photodiodes 600 of the pixels 303 in all rows
is started (corresponding to the still image accumulation period
661 in FIG. 35).
Further, during the accumulation period of signal charge of the
first moving image, the readout period of the m-th row of the
second moving image in the previous shooting period that ends at
time t1 is completed.
First, at time t15, the reset pulse .PHI.RES(m) for the m-th row
supplied from the vertical scanning circuit 307 is changed from the
high level to the low level. This causes the reset transistor 604
of each pixel 303 in the m-th row to be turned off to release the
reset state of the floating diffusion region 608. Simultaneously, a
select pulse .PHI.SEL(m) for the m-th row supplied from the
vertical scanning circuit 307 is changed from the low level to the
high level. This causes the select transistor 606 of each pixel 303
in the m-th row to be turned on to enable the readout of the image
signal from each pixel 303 in the m-th row.
Then, at time t16, a transfer pulse .PHI.TX2B(m) for the m-th row
is changed from the low level to the high level. This causes the
transfer transistor 602B of each pixel 303 in the m-th row to be
turned on to transfer, to the floating diffusion region 608, the
signal charge of the second moving image accumulated in the signal
holding unit 607B during the previous shooting period that ends at
time t1. As a result, a signal corresponding to a change in the
potential of the floating diffusion region 608 is read out into the
signal output line 623 via the amplifier transistor 605 and the
select transistor 606. The signal read out into the signal output
line 623 is supplied to an unillustrated readout circuit, and
output to the outside as an image signal of the second moving image
of each pixel in the m-th row (corresponding to the moving image
readout period 666 in FIG. 35).
Thus, the readout of the second moving image in the previous
shooting period that ends at time t1 is completed. Next, the
readout of the first moving image in the shooting period that
starts at time t1 is performed (corresponding to the still image
readout period 665 in FIG. 35).
Then, at time t17, the transfer pulse .PHI.TX2B(m) for the m-th row
is changed from the low level to the high level. This causes the
transfer transistor 602B of each pixel 303 in the m-th row to be
turned on. At this time, the reset pulse .PHI.RES(m) in the m-th
row is already changed to the high level, and hence the reset
transistor 604 is in the on-state. Thus, the floating diffusion
region 608 of each pixel 303 in the m-th row, and the signal
holding unit 607B of each pixel 303 in the m-th row are reset. At
this time, the select pulse .PHI.SEL(m) in the m-th row is also
changed to the low level, and each pixel in the m-th row is
returned to the unselected state.
Then, at time t18, the reset pulse .PHI.RES(1) for the first row is
changed from the high level to the low level. This causes the reset
transistor 604 of each pixel 303 in the first row to be turned off
to release the reset of the floating diffusion region 608.
Simultaneously, the select pulse .PHI.SEL(1) for the first row is
changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the first row to be
turned on to enable the readout of an image signal from each pixel
303 in the first row.
Then, immediately before time t19, transfer pulses .PHI.TX1A
(.PHI.TX1A(1), .PHI.TX1A(m)) for all rows supplied from the
vertical scanning circuit 307 are changed from the low level to the
high level. This causes the transfer transistors 601A of the pixels
303 in all rows to be turned on to transfer, to the signal holding
units 607A, the signal charges accumulated in the photodiodes 600
of the pixels 303 in all rows (corresponding to the still image
transfer period 662 in FIG. 35).
At time t19, the transfer pulses .PHI.TX1A (.PHI.TX1A(1),
.PHI.TX1A(m)) for all rows are changed from the high level to the
low level. This causes the transfer transistors 601A of the pixels
303 in all rows to be turned off to complete the transfer of the
signal charges accumulated in the photodiodes 600 of the pixels 303
in all rows to the signal holding units 607A.
A period from time t14 to time t19 corresponds to the accumulation
time (T1) of the first moving image in the shooting period that
starts at time t1. In this driving example, since the number of
accumulation periods of the first moving image in one shooting
period is once, the accumulation time of the first moving image is
the same as the time corresponding to the accumulation period.
Then, at time t20, the transfer pulse .PHI.TX2A(1) for the first
row is changed from the low level to the high level. This causes
the transfer transistor 602A of each pixel 303 in the first row to
be turned on to transfer, to the floating diffusion region 608, the
signal charge accumulated in the signal holding unit 607A of each
pixel 303 in the first row. As a result, a signal corresponding to
a change in the potential of the floating diffusion region 608 is
read out into the signal output line 623 via the amplifier
transistor 605 and the select transistor 606 of each pixel 303 in
the first row. The signal read out into the signal output line 623
is supplied to an unillustrated readout circuit, and output to the
outside as an image signal of the first moving image of each pixel
in the first row (corresponding to the still image readout period
665 in FIG. 35).
Then, the seventh accumulation period of the second moving image is
started at time t21. Here, the start time t21 of the seventh
accumulation period of the second moving image is set to a time
after a lapse of time T (=(7+2).times.2.times.Th+Tb) from time t1
at which the vertical synchronization signal .PHI.V becomes the
high level. In this driving example, two accumulation periods of
the second moving image overlap the accumulation period of the
first moving image (corresponding to the still image accumulation
period 661 in FIG. 35). Therefore, the start time t21 of the
seventh accumulation period of the second moving image is
equivalent to the start time of the ninth accumulation period of
the second moving image in the shooting period that starts at time
t1.
Since the operation of the seventh accumulation period of the
second moving image starting at time t21 and ending at time t23 is
the same as the operation of the first accumulation period of the
second moving image starting at time t5 and ending at time t7 as
mentioned above, the description thereof will be omitted.
Then, during a period from time t23 to time t24, the eighth to
thirteenth accumulation periods of the second moving image are
performed in the same manner as the period from time t5 to time t7
as mentioned above.
Then, the final fourteenth accumulation period of the second moving
image in the shooting period that starts at time t1 is started at
time t24. Here, the start time t24 of the fourteenth accumulation
period of the second moving image is set to a time after a lapse of
time T (=(14+2).times.2.times.Th+Tb) from time t1 at which the
vertical synchronization signal .PHI.V becomes the high level.
Since the operation of the fourteenth accumulation period of the
second moving image starting at time t24 and ending at time t26 is
the same as the operation of the first accumulation period of the
second moving image starting at time t5 and ending at time t7 as
mentioned above, the description thereof will be omitted. In the
shooting mode, the period to perform the Np accumulation periods of
the second moving image is a period from time t5 to time t26.
Then, at time t27, the reset pulse .PHI.RES(m) for the m-th row is
changed from the high level to the low level. This causes the reset
transistor 604 of each pixel 303 in the m-th row to be turned off
to release the reset state of the floating diffusion region 608.
Simultaneously, the select pulse .PHI.SEL(m) for the m-th row is
changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the m-th row to be
turned on to enable the readout for the image signal from each
pixel 303 in the m-th row.
Then, at time t28, the transfer pulse .PHI.TX2A(m) for the m-th row
is changed from the low level to the high level. This causes the
transfer transistor 602A of each pixel 303 in the m-th row to be
turned on to transfer, to the floating diffusion region 608, the
signal charge of the first moving image accumulated in the signal
holding unit 607A of each pixel 303 in the m-th row. As a result, a
signal corresponding to a change in the potential of the floating
diffusion region 608 is read out into the signal output line 623
via the amplifier transistor 605 and the select transistor 606 of
each pixel 303 in the m-th row. The signal read out into the signal
output line 623 is supplied to an unillustrated readout circuit,
and output to the outside as an image signal of the first moving
image of each pixel in the m-th row (corresponding to the still
image readout period 665 in FIG. 35).
Then, at time t29, the vertical synchronization signal .PHI.V
supplied from the timing generation unit 189 is changed from the
low level to the high level to start the next shooting period.
As described above, in the first moving image/still image shooting
mode, the end time of the accumulation period of the first moving
image is fixed with respect to the vertical synchronization signal,
and the start time of the accumulation periods of the second moving
image performed plural times in one shooting period is fixed with
respect to the vertical synchronization signal. This enables the
readout of the first moving image and the second moving image
within the same shooting period.
Therefore, when the shutter speed T1 of the first moving image is
slower than the predetermined shutter speed Tth, the first moving
image short in accumulation time and having no blur, and the second
moving image long in accumulation period and with less jerkiness
can be shot in one shooting period at the same time.
FIG. 37 is a chart for describing the accumulation and readout
timings of the imaging element 184 in the imaging device of the
present embodiment when the first moving image and the second
moving image are shot at the same time in the second moving
image/still image shooting mode capable of shooting a moving image
without rolling distortion. The term "accumulation" here means
operation for transferring and accumulating charge generated in the
photodiode 600 to and in the signal holding units 607A, 607B. The
term "readout" means operation for outputting signals based on the
electric charges, held in the signal holding units 607A, 607B, to
the outside of the imaging element 184 via the floating diffusion
region 608.
In FIG. 37, the abscissa is expressed in time to illustrate a
vertical synchronization signal 650, a horizontal synchronization
signal 651, a still image accumulation period 661, a still image
transfer period 662, a still image readout period 665, a moving
image accumulation period 663, a moving image transfer period 664,
and a moving image readout period 666. In this driving example, the
first moving image and the second moving image are read out during
each cycle of the vertical synchronization signal 650. Further,
timings of 16 rows are illustrated in FIG. 37 for descriptive
purposes, but the actual imaging element 184 has thousands of rows.
In FIG. 37, the final row is the m-th row.
The first moving image is generated based on signal charge
generated during one accumulation period (still image accumulation
period 661) performed simultaneously in all rows during each cycle
(time Tf) of the vertical synchronization signal 650. The second
moving image is generated based on signal charge obtained by adding
up signal charges respectively generated during accumulation
periods (moving image accumulation periods 663) divided by the
number of Np times (where Np is an integer of 2 or more (Np>1)).
Np as the number of accumulation periods of the second moving image
performed during one shooting period is, for example, eight times,
and these accumulation periods are performed in all rows at equal
time intervals during the readout period (still image readout
period 665) of the first moving image. The interval (time Tf) of
the vertical synchronization signal 650 corresponds to the frame
rate of the moving image, which is 1/60 second in this driving
example. Further, the accumulation of the first moving image is
performed during the readout of the second moving image (moving
image readout period 666) in one shooting period.
This enables shooting of the first moving image and the second
moving image at the same time. An image having no blur can also be
acquired as the first moving image at a short accumulation time
intended by the person who performs shooting. Further, Np times of
accumulation periods performed at equal time intervals virtually
mean one long accumulation period from the start time of the first
accumulation period to the end time of the Np-th accumulation
period. Therefore, an image with less jerkiness and without rolling
distortion can be acquired as the second moving image.
In the previous shooting period that ends at time t51 in FIG. 37,
the accumulation period of the first moving image (still image
accumulation period 661) is set to a time corresponding to a
shutter speed T2 set by the person who performs shooting. In this
driving example, the shutter speed T2 is set to 1/2000 second. The
center time of the accumulation period of the first moving image is
the same in all rows (a time after a lapse of time Tc from the
vertical synchronization signal 650), which is so set that the
accumulation period will be completed before the readout period of
the first row of the first moving image (still image readout period
665). Here, since the time Tc up to the center time of the
accumulation period of the first moving image is the same in all
rows, the start time and end time of the accumulation period of the
first moving image with respect to the vertical synchronization
signal 650 are set depending on the shutter speed T2 of the first
moving image. The time Tc up to the center time of the accumulation
period of the first moving image is set to be the center of the
readout period of the second moving image (moving image readout
period 666), which is set to be about 1/4 of the time Tf
corresponding to the interval of the vertical synchronization
signal 650.
On the other hand, the accumulation period of the second moving
image (moving image accumulation period 663) is performed plural
times at equal time intervals during the readout period of the
first moving image (still image readout period 665). In this
driving example, the time interval is set to complete the
accumulation period divided into eight times immediately before the
start of the readout period of the first row of the second moving
image (moving image readout period 666). The time interval of the
accumulation period of the second moving image is set to be a
multiple of an integer for the interval Th of the horizontal
synchronization signal 651. Thus, the Np accumulation periods of
all rows of the second moving image become the same. In FIG. 37,
the time interval of the accumulation period of the second moving
image is illustrated to be twice the interval Th of the horizontal
synchronization signal 651 for descriptive purposes. When the
number of rows of the imaging element 184 is denoted by m, and the
number of accumulations of the second moving image during each
cycle is denoted by Np, the time interval of the accumulation
period of the second moving image is generally set to a value
obtained by multiplying an integer not exceeding m/Np by the
interval Th of the horizontal synchronizing signal 651.
Further, one accumulation time of the second moving image is set to
T2/Np (= 1/16000 second). The start time of the accumulation period
of the second moving image in all rows is fixed with respect to the
vertical synchronization signal 650. The end time of one
accumulation period of the second moving image is set with respect
to the vertical synchronization signal 650 depending on the shutter
speed T2 of the first moving image set by the person who performs
shooting.
It is also effective that the dead time of the second moving image
generated during the previous shooting period that ends at time t51
is corrected using the first moving image generated in this
shooting period.
Thus, the accumulation period of the second moving image is
performed in all rows at the same timing during the readout period
of a still image (still image readout period 665) so that a moving
image without rolling distortion can be acquired.
Referring next to a timing chart of FIG. 38, an example of the
control method for the imaging element 184 in a shooting period
starting at time t51 in FIG. 37 will be described. Time t51 at
which a vertical synchronization signal .PHI.V rises in FIG. 38 is
the same as time t51 at which the vertical synchronization signal
.PHI.V 650 rises in FIG. 37.
It is assumed here that the imaging element 184 has m rows of
pixels in the vertical direction. In FIG. 38, the timings of the
first row and the m-th row as the final row are illustrated among
the m rows. In FIG. 38, a signal .PHI.VV is the vertical
synchronization signal, and a signal .PHI.VH is the horizontal
synchronization signal.
First, at time t51, the vertical synchronization signal .PHI.V and
the horizontal synchronization signal .PHI.H supplied from the
timing generation unit 189 are changed from the low level to the
high level.
Then, at time t52 synchronized with the change of the vertical
synchronization signal .PHI.V to the high level, a reset pulse
.PHI.RES(1) for the first row supplied from the vertical scanning
circuit 307 is changed from the high level to the low level. This
causes the reset transistor 604 of each pixel 303 in the first row
to be turned off to release the reset state of the floating
diffusion region 608. Simultaneously, a select pulse .PHI.SEL(1)
for the first row supplied from the vertical scanning circuit 307
is changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the first row to be
turned on to enable the readout of an image signal from each pixel
303 in the first row.
Then, at time t53, a transfer pulse .PHI.TX2B(1) for the first row
supplied from the vertical scanning circuit 307 is changed from the
low level to the high level. This causes the transfer transistor
602B of each pixel 303 in the first row to be turned on to
transfer, to the floating diffusion region 608, signal charge of
the second moving image accumulated in the signal holding unit 607B
during the previous shooting period (a shooting period completed at
time t51). As a result, a signal corresponding to a change in the
potential of the floating diffusion region 608 is read out into the
signal output line 623 via the amplifier transistor 605 and the
select transistor 606. The signal read out into the signal output
line 623 is supplied to an unillustrated readout circuit, and
output to the outside as an image signal of the second moving image
of each pixel in the first row (corresponding to the moving image
readout period 666 in FIG. 37).
Then, at time t54, a transfer pulse .PHI.TX2B(1) for the first row
and transfer pulses .PHI.TX2A (.PHI.TX2A(1), .PHI.TX2A(m)) for all
rows supplied from the vertical scanning circuit 307 are changed
from the low level to the high level. This causes the transfer
transistor 602B of each pixel 303 in the first row and the transfer
transistors 602A of the pixels 303 in all rows to be turned on. At
this time, the reset pulses .PHI.RES (.PHI.RES(1), .PHI.RES(m)) in
all rows are already changed to the high level, and hence the reset
transistors 604 are in the on-state. Thus, the floating diffusion
regions 608 of the pixels 303 in all rows, the signal holding units
607A of the pixels 303 in all rows, and the signal holding unit
607B of each pixel 303 in the first row are reset. At this time,
the select pulse .PHI.SEL(1) in the first row is also changed to
the low level, and each pixel 303 in the first row is returned to
the unselected state.
Then, the accumulation period of the first moving image is
performed from time t55. In this driving example, the number of
accumulation periods of the first moving image in one shooting
period is once. The center time of the accumulation period of the
first moving image is the same in all rows (a time after a lapse of
time Tc from the vertical synchronization signal 650), which is so
set that the accumulation period will be completed before the
readout period of the first row of the first moving image (still
image readout period 665). Here, since the time Tc up to the center
time of the accumulation period of the first moving image is the
same in all rows, the start time and end time of the accumulation
period of the first moving image with respect to the vertical
synchronization signal 650 are set depending on a shutter speed T2
of the first moving image set by the person who performs
shooting.
At time t55 back by time T2/2 from time t56 as the center time of
the accumulation period of the first moving image, transfer pulses
.PHI.TX3 (.PHI.TX3(1), .PHI.TX3(m)) for all rows are changed from
the high level to the low level. This causes the transfer
transistors 603 of the pixels 303 in all rows to be turned off to
release the reset of the photodiodes 600 of the pixels 303 in all
rows. Then, in the photodiodes 600 of the pixels 303 in all rows,
the accumulation period of signal charge of the first moving image
is started (corresponding to the still image accumulation period
661 in FIG. 37). Here, a period from time t51 to time t56
corresponds to time Tc in FIG. 37. Further, the accumulation of the
signal charge of the first moving image is completed before the end
of the readout period of the second moving image in the m-th row
during a shooting period until time t51 (corresponding to the
moving image readout period 666 in FIG. 37).
Then, immediately before time t57, transfer pulses .PHI.TX1A
(.PHI.TX1A(1), .PHI.TX1A(m)) for all rows supplied from the
vertical scanning circuit 307 are changed from the low level to the
high level. This causes the transfer transistors 601A of the pixels
303 in all rows to be turned on to transfer, to the signal holding
units 607A, signal charges accumulated in the photodiodes 600 of
the pixels 303 in all rows (corresponding to the still image
transfer period 662 in FIG. 37).
Then, at time t57, the transfer pulses .PHI.TX1A (.PHI.TX1A(1),
.PHI.TX1A(m)) for all rows are changed from the high level to the
low level. This causes the transfer transistors 601A of the pixels
303 in all rows to be turned off to complete the transfer of the
signal charges accumulated in the photodiodes 600 to the signal
holding units 607A.
A period from time t55 to time t57 corresponds to the accumulation
time (shutter speed T2) of the first moving image in the shooting
period that starts at time t51 in FIG. 37. In this driving example,
since the number of accumulation periods of the first moving image
in one shooting period is once, the accumulation time of the first
moving image in one shooting period is the same as the accumulation
period.
Then, at time t58, a reset pulse .PHI.RES(m) for the m-th row is
changed from the high level to the low level. This causes the reset
transistor 604 of each pixel 303 in the m-th row to be turned off
to release the reset state of the floating diffusion region 608.
Simultaneously, a select pulse .PHI.SEL(m) for the m-th row is
changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the m-th row to be
turned on to enable the readout of an image signal from each pixel
303 in the m-th row.
Then, at time t59, a transfer pulse .PHI.TX2B(m) for the m-th row
supplied from the vertical scanning circuit 307 is changed from the
low level to the high level. This causes the transfer transistor
602B of each pixel 303 in the m-th row to be turned on to transfer,
to the floating diffusion region 608, signal charge of the second
moving image accumulated in the signal holding unit 607B during the
previous shooting period (a shooting period until time t51 in FIG.
37). As a result, a signal corresponding to a change in the
potential of the floating diffusion region 608 is read out into the
signal output line 623 via the amplifier transistor 605 and the
select transistor 606. The signal read out into the signal output
line 623 is supplied to an unillustrated readout circuit, and
output to the outside as an image signal of the second moving image
of each pixel in the m-th row (corresponding to the moving image
readout period 666 in FIG. 37).
Then, at time t60, the transfer pulse .PHI.TX2B(m) for the m-th row
is changed from the low level to the high level. This causes the
transfer transistor 602B of each pixel 303 in the m-th row to be
turned on. At this time, the reset pulse .PHI.RES(m) for the m-th
row is already changed to the high level, and hence the reset
transistor 604 is in the on-state. Thus, the floating diffusion
regions 608 of each pixel 303 in the m-th row and the signal
holding unit 607B of each pixel 303 in the m-th row are reset. At
this time, the select pulse .PHI.SEL(m) in the m-th row is also
changed to the low level, and each pixel 303 in the m-th row is
returned to the unselected state.
When the readout of a moving image as the second image in the
previous shooting period that ends at time t51 is completed, the
readout of the first moving image in the shooting period that start
at time t51 (corresponding to the still image readout period 665 in
FIG. 37) is started. Further, the accumulation of the second moving
image (corresponding to the moving image accumulation period 663 in
FIG. 37) is started.
At time t61, the reset pulse .PHI.RES(1) for the first row is
changed from the high level to the low level. This causes the reset
transistor 604 of each pixel 303 in the first row to be turned off
to release the reset state of the floating diffusion region 608.
Simultaneously, the select pulse .PHI.SEL(1) for the first row is
changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the first row to be
turned on to enable the readout of an image signal from each pixel
303 in the first row.
Then, at time t62, the transfer pulse .PHI.TX2A(1) for the first
row is changed from the low level to the high level. This causes
the transfer transistor 602A of each pixel 303 in the first row to
be turned on to transfer, to the floating diffusion region 608,
signal charge accumulated in the signal holding unit 607A of each
pixel 303 in the first row. As a result, a signal corresponding to
a change in the potential of the floating diffusion region 608 is
read out into the signal output line 623 via the amplifier
transistor 605 and the select transistor 606 of each pixel 303 in
the first row. The signal read out into the signal output line 623
is supplied to an unillustrated readout circuit, and output to the
outside as an image signal of the first moving image in the first
row (corresponding to the still image readout period 665 in FIG.
37).
Then, at time t63, the transfer pulses .PHI.TX3 (.PHI.TX3(1),
.PHI.TX3(m)) for all rows are changed from the high level to the
low level. This causes the transfer transistors 603 of the pixels
303 in all rows to be turned off to release the reset of the
photodiodes 600 of the pixels 303 in all rows so as to start the
accumulation of signal charge in the photodiodes 600 (corresponding
to the moving image accumulation period 663 in FIG. 37).
Here, a time interval Tb between time t51, at which the vertical
synchronization signal .PHI.V becomes the high level, and time t63,
at which the accumulation of signal charge in the photodiodes 600
of the pixels 303 in all rows is started, is fixed.
Then, immediately before time t64, transfer pulses .PHI.TX1B
(.PHI.TX1B(1), .PHI.TX1B(m)) for all rows supplied from the
vertical scanning circuit 307 are changed from the low level to the
high level. This causes the transfer transistors 601B of the pixels
303 in all rows to be turned on to transfer, to the signal holding
units 607B, the signal charges accumulated in the photodiodes 600
of the pixels 303 in all rows corresponding to the moving image
transfer period 664 in FIG. 37).
Then, at time t64, the transfer pulses .PHI.TX1B (.PHI.TX1B(1),
.PHI.TX1B(m)) for all rows are changed from the high level to the
low level. This causes the transfer transistors 601B of the pixels
303 in all rows to be turned off to complete the transfer of the
signal charges accumulated in the photodiodes 600 to the signal
holding units 607B.
A period from time t63 to time t64 corresponds to the accumulation
time (=T2/8) in one accumulation period for the second moving
image.
Similarly, at time t64, the transfer pulses .PHI.TX3 (.PHI.TX3(1),
.PHI.TX3(m)) for all rows are changed from the low level to the
high level. This causes the transfer transistors 603 of the pixels
303 in all rows to be turned on to put the photodiodes 600 of the
pixels 303 in all rows into the reset state.
The second accumulation period of the second moving image is
started at time t65 after a lapse of the time twice the interval Th
of the horizontal synchronization signal .PHI.H from the start time
t63 of the first accumulation period of the second moving image in
the shooting period that starts at time t51.
Since the operation of the second accumulation period of the second
moving image starting at time t65 and ending at time t66 is the
same as the operation of the first accumulation period of the
second moving image starting at time t63 and ending at time t64 as
mentioned above, the description thereof will be omitted.
Here, in the operation of the first and the second accumulation
periods of the second moving image, signal charges of the second
moving image generated during these two accumulation periods are
added up and held in the signal holding unit 607B.
Then, during a period from time t66 to time t67, the third to
seventh accumulation periods of the second moving image are
performed in the same manner as the period from time t63 to time
t64 as mentioned above.
Then, the eighth accumulation period of the second moving image as
the final period in one shooting period is started at time t67.
Here, the start time t67 of the eighth accumulation period of the
second moving image is set to the time after a lapse of the time T
(=8.times.2.times.Th+Tb) from time t51 at which the vertical
synchronization signal .PHI.V becomes the high level. Here, Th
denotes the time interval of the horizontal synchronization signal
.PHI.H, and Tb denotes a time interval between time t51 at which
the vertical synchronization signal .PHI.V becomes the high level
and time t63 at which the first accumulation period of the second
moving image is started in the photodiode 600.
Since the operation of the eighth accumulation period of the second
moving image starting at time t67 and ending at time t68 is the
same as the operation of the first accumulation period of the
second moving image starting at time t63 and ending at time t64 as
mentioned above, the description thereof will be omitted.
The period from time t63 to time t68 is the period of accumulating
signal charge for the second moving image in the shooting mode,
which is performed during the readout period of the first moving
image (a period from time t62 to time t70).
At time t69, at which the accumulation period of the second moving
image is completed, the reset pulse .PHI.RES(m) for the m-th row is
changed from the high level to the low level. This causes the reset
transistor 604 of each pixel 303 in the m-th row to be turned off
to release the reset state of the floating diffusion region 608.
Simultaneously, the select pulse .PHI.SEL(m) for the m-th row is
changed from the low level to the high level. This causes the
select transistor 606 of each pixel 303 in the m-th row to be
turned on to enable the readout of an image signal from each pixel
303 in the m-th row.
Then, at time t70, the transfer pulse .PHI.TX2A(m) for the m-th row
is changed from the low level to the high level. This causes the
transfer transistor 602A of each pixel 303 in the m-th row to be
turned on to transfer, to the floating diffusion region 608, the
signal charge accumulated in the signal holding unit 607A of each
pixel 303 in the m-th row. As a result, a signal corresponding to a
change in the potential of the floating diffusion region 608 is
read out into the signal output line 623 via the amplifier
transistor 605 and the select transistor 606 of each pixel 303 in
the m-th row. The signal read out into the signal output line 623
is supplied to an unillustrated readout circuit, and output to the
outside as an image signal of the first moving image of each pixel
in the m-th row (corresponding to the still image readout period
665 in FIG. 37).
Then, at time t71, the vertical synchronization signal .PHI.V
supplied from the timing generation unit 189 is changed from the
low level to the high level to start the next shooting period.
As described above, in the second moving image/still image shooting
mode, the accumulation period of the second moving image is
performed in all rows at the same timing during readout period of
the first moving image (still image readout period 665). Thus, a
moving image without rolling distortion can be acquired. Further,
since the accumulation period of the second moving image is set
longer than the accumulation period of the first moving image, an
image with less jerkiness can be acquired.
As described above, according to the present embodiment, "picture
A" having the stop motion effect and "picture B" with less
jerkiness can be acquired at the same time. The image presentation
method as illustrated in the first embodiment can be used for two
moving images difference in characteristics to provide an image
suitable for viewing of both of moving image/still image when two
or more images are shot at the same time and viewed using the
single imaging element 184.
Alternative Embodiments
The present invention is not limited to the aforementioned
exemplary embodiments, and various modifications can be made.
For example, the configuration of the imaging device described in
the aforementioned embodiments is just an example, and an imaging
device to which the present invention can be applied is not limited
to the configuration illustrated in FIG. 1A to FIG. 2. Further, the
circuit configuration of each unit of the imaging element is not
limited to the configuration illustrated in FIG. 3, FIG. 8, FIG.
11, FIG. 32, or the like.
Further, in the above first embodiment, the example of performing
crosstalk correction on "picture A" and "picture B" is illustrated
as the preferred mode, but the crosstalk correction is not
necessarily required.
Further, in the above first embodiment, the example of shooting
"picture A" and "picture B" at the same frame rate is illustrated,
"picture A" and "picture B" are not necessarily required to be at
the same frame rate. In this case, for example, at least one of
plural frames of "picture A" shot within one frame period of
"picture B" can be associated with the frame of "picture B."
Further, in the above third embodiment, the accumulation period of
the first moving image is performed once, and the accumulation
period of the second moving image is performed sixteen times or
eight times. However, the number of accumulation periods is
selected appropriately according to the shooting conditions and the
like, and not limited thereto. For example, the number of
accumulations of the first moving image may be at least once, or
may be twice or more. Further, the number of accumulations of the
second moving image may be at least twice or more.
Embodiment(s) of the present invention can also be realized by a
computer of a system or apparatus that reads out and executes
computer executable instructions (e.g., one or more programs)
recorded on a storage medium (which may also be referred to more
fully as a `non-transitory computer-readable storage medium`) to
perform the functions of one or more of the above-described
embodiment(s) and/or that includes one or more circuits (e.g.,
application specific integrated circuit (ASIC)) for performing the
functions of one or more of the above-described embodiment(s), and
by a method performed by the computer of the system or apparatus
by, for example, reading out and executing the computer executable
instructions from the storage medium to perform the functions of
one or more of the above-described embodiment(s) and/or controlling
the one or more circuits to perform the functions of one or more of
the above-described embodiment(s). The computer may comprise one or
more processors (e.g., central processing unit (CPU), micro
processing unit (MPU)) and may include a network of separate
computers or separate processors to read out and execute the
computer executable instructions. The computer executable
instructions may be provided to the computer, for example, from a
network or the storage medium. The storage medium may include, for
example, one or more of a hard disk, a random-access memory (RAM),
a read only memory (ROM), a storage of distributed computing
systems, an optical disk (such as a compact disc (CD), digital
versatile disc (DVD), or Blue-ray Disc (BD).TM.), a flash memory
device, a memory card, and the like.
While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is
not limited to the disclosed exemplary embodiments. The scope of
the following claims is to be accorded the broadest interpretation
so as to encompass all such modifications and equivalent structures
and functions.
* * * * *